I think if you take the time to analyze the facts your answer will be a no brainer. Fact- A kitchen makeover is without question one of the largest and most expensive projects you can undertake in your home. Fact-The sink is without question the singular focal point of the kitchen. Almost every time you go in the kitchen, regardless of what the reason, you will ultimately end up at the sink if only to grab a glass of water. Fact- If you have your heart set o a 10" sink and settle for an 8" sink it will forever be a source of irritation and contention, one which you will confront dozens of times a day. Fact-If you are changing all the cabinets you will already have easy access to the wall and changing the drain line is no big deal. Fact-If you install the 8" sink now, then later decide you really want the 10" sink it could prove nearly cost prohibitive to make the necessary changes to the drain lines. Now let us consider what would be required to lower the drain while you have access to the wall. In a best case scenario when the fixture arm enters the wall it is connected to a vertical line by means of a sanitary tee. In that case it would be very easy to cut the line, lower the tee to the desired level and reconnect the line. In a worst case scenario the waste arm enters the wall then turns horizontal and runs through the wall to a point were it connects to a vertical stack. The question then becomes how far does the horizontal line travel through the wall? Under the IRC a kitchen sink drain line is an 1-1/2" line and it is allowed to run a maximum of 6' from the trap weir to the vent opening. Allowing that there is generally about 12" from the wall to the trap that means that the line could run up to 5' horizontally in the wall. Under the UPC we are required to use a 2" diameter drain line but the total developed length from trap weir to vent opening of a 2" fixture arm is limited to only 5' so we could anticipate a maximum of 4" horizontally in the wall. In all probability the portion of the wall that you would need to open up will most likely be covered by the cabinets when all done, therefore when you open the sheet rock it would only require a simple patch with one coat of mud & tape to prevent bugs from entering. Not a big deal here. The question then becomes how much should you lower the line? From your preliminary calculations you determined that you need approximately 2" however, from my experience it is much easier if we allow ourselves plenty of room, therefore I would lower the arm at least 4 or perhaps 5". Keep in mind that code will allow up to 12" vertical drop from the finished sink opening to the water level in the trap.

I have the Franke Orca that Debs3 linked to and I do LOVE it. for the just the reason you mention. Because it has shelves, things can be put on one side up off the bottom of the sink, stay out of the mess/water and drain if needed. I can put a shelf on the left or right about half way up. The bottom grid means I can even put items around the GD and it is still useful and accessable. I have been known to put clean dishes on the top shelf on the right, slide a few dirty ones under them on the same side and still have a bowl I am working in on the left and use the GD while I do it! I don't have a prep sink so this one has to do everything! I had my sink bumped out a couple of inches, but because of the shape, it does leave room for a faucet on the side that is slightly narrower. Don't know how you feel about ordering over the internet but I paid less than 700.00 for this sink, so it can't possibly be 700.00 more than the sink you are considering. Of coarse the accessories are extra, and they are a bit pricey, but you can always add them later. I have to admitt, even with good discounts from faucet depot, the sink and all accessories, including bottom grid, two half shelfs because each side is a different size, and the collander ran about a 1000.00 buying everything at once. VERY versatile, though. Sue

Can you create a small 2" thick mounting block to put behind the posts to bring the towel bar forward? Cut a circle the same size of the post so you don't really see it or make it larger so you could router a decorative edge on it to make it look intentional or bevel it so it seems to melt into the wall .

Did you buy a new sink and cabinet? If you have the cabinet out, it is usually not too difficult for a plumber (or maybe a good handyman) to open the wall and cut into the vertical drain pipe and move the sink drain connection to a lower point on the pipe. Assuming the vent pipe runs up, it can stay in its current location. The fitting mounted lower on the drain pipe would allow more space to fit the trap for a deeper sink. Wall repair is relatively simple because its all going to be hidden under the sink area where a wall patch won't even be visible. If you look at this picture you can see how it is typically connected and vented. https://inspectapedia.com/plumbing/Plumbing-Vent-Distance-Codes.php The plumber would just move the connection lower on the vertical pipe. If you do have issues with reconnecting the vent, you should be able to use a studor vent (air admittance valve) as a replacement. Bruce