debrak2008, I have to figure out how to post a pic here first :P. But the countertop is those yellowish cultured marble top (you see a lot of those in the older houses) but it's not one-piece. The sink is an undermount sink, so it's just like the typical granite top with undermount sink you see now. BUT mine is not granite top obviously, and the sink is rusty and scratched. sjhockeyfan and weedyacres, Thanks for your link! Yes I looked on craigslist and saw some ads for prefab granite tops too. And my friend told me about this too. But my problem is I can't find my size, esp. the 72 inch SINGLE sink countertop... :(. And if I custom made that one, it's expensive. The worst is that I need one 60 inch (I found that this countertop is the only one that's the most typical size) and one 72 inch that's matching right, cuz they're in the same jack & jill bathroom! For the 36 inch countertop for the half bath, the problem is the depth is 1 inch more shallow than the typical tops, so it's 20 inch. And I can't go any deeper because the top is right next to the door opening so 21" countertop won't work! So yes, my house has some strange bathrooms and I figured either we spent more money to hire someone to renovate (but we don't have that funds now) the bathrooms, or we try to make small changes. Of course, I wish I could be as handy as most of the members here then the problem can be solved easily :( Anyways, thanks for all your answers! Please do share if you have any more insights. Thanks again!

I currently have top mount sink and it does not have to be replaced. I was just thinking that a particular faucet that I may like may not fit the current sink but would fit a new sink. You guys make an excellent point, however, because I would prefer an under mount sink w/ new countertops.

To answer your question, yes. A larger cutout can be made on site without dust or mess; we do this every day. You can undermount a sink as large as your base cabinet no matter what the sink manufacturers say, you just have to strap your sink in place. The cost effectiveness of changing your sink depends upon the size of your kitchen, the layout, and the rarity of your stone and how much you like it.

No harm will come to the cabinet or countertop when the blocking holding the sink is removed. Drive a stiff scraper between the sink flange and the stone bottom and the sink will drop. Clean the bottom of the stone and install a Hercules Universal Sink Harness or a Sink Strap or two to the cabinet sides. Silicone the sink flange, clamp the sink in place through the drain hole, check the reveal, tighten the Harness/Strap, and remove the clamp.