A lighting designer's most often specified MR16 lamp is the GE Precise Constant Color. I believe they were the first with a coating technology that didn't degrade and color shift. Others like Sylvania came out with Tru-Aim and now almost everyone has a name for their upgraded lamp choice with a more stable reflector coating. Cheaper lamp coatings can produce poor colorings right from the start with a greenish fringe. Cheap lamp coatings degrade losing both lumen output from the fixture and shifting to an awful color.

Philips and Sylvania now have coatings which turn more heat into light. Philips calls theirs Energy Advantage IRC and they had more variety of lamps available last I looked. This will be your best lamp choice with energy efficiency in mind. The GE constant color is still the best for an even beam of light. Some of the IRC lamps have a hot spot right in the center. You can add a diffusion lens to smooth out a hot spot if noticeable. These types of lenses come standard in high quality recessed fixtures like Cooper Iris and Juno Aculux but I've never seen one standard in a track fixture.

I'm dont' know from your description what lamps you have since many can be called incandescent floods. If you have a R30 or BR30 then these are now only available in 65 watt. Only halogen Par 30 come in 75. An R lamp has a poor quality painted coating and flood R30s produce a very wide beam of light. Any Par or MR16 lamp is going to produce a more controlled beam. What this means is that you may need more fixtures to overlap beams of light and evenly light your kitchen. You should try the 45 watt 60 degree, depending on the fixture.

Here is a link that might be useful: click on Energy Advantage IRC MR16 Lamps

If your existing lamps are 75r30 or 65br30 , you can replace each with a 50mr16fl(EXN) and expect more light output.
Nearly all good MR16's are 3000K , so unless you want to order 4100K or 5000K,giving you a cooler or bluer light, stay with a good MR16 lamp...GE,Philips,Iwasaki,for example.

A 50w halogen MR16 (or the enhanced/infrared 35w versions) is nearly as bright as old non-halogen incandescent 75w R30 or R40 floodlamp bulbs. Look for wide-flood bulbs, about 55° beam spread, for general lighting use. The light produced by 12-volt halogen bulbs is noticeably whiter than what you're used to, which makes colors slightly more vibrant, which is perceived by the human eye as brighter.

(Lighting experts may dispute my last statement, noting that both low-voltage halogen MR16s and incandescent line-voltage lamps have the same, perfect color rendering index (CRI) of 100 - CRI has long been the standard industry metric for measuring color rendition and differentiation - but CRI has increasingly been shown not to correlate well with actual perception of lighting quality. In real life, people and things illuminated by halogen MR16s look better than when illuminated by line-voltage halogen bulbs, which in turn look better than when non-halogen incandescents are used. (Fluorescent bulbs are all over the map light-quality-wise.)

LED MR16s are now available too. I doubt they're as bright or good-looking as halogens yet, but that's likely to change in the next few years given the Moore's Law-like increases in LED brightness since the relatively recent invention of white LEDs. LEDs have huge advantages in longevity, coolness, and efficiency.

Thanks and just to followup-- we installed eight little track bullets and the GE Precise Constant Color with the 55 angle spread, and new dimmers that work with the electronic MR 16 fixtures. The light is so much better than what we had before. We're quite happy-- thanks for all the pointers here!

LEDs have huge advantages in longevity, coolness, and efficiency.

Only the very high quality ones, and even those can't yet beat good linear fluorescents for efficiency.

Worse, there are many cheap LED lights which produce poor quality light, are barely (if any) more efficient than incandescents, and are short-lived. This is especially true of cheap retrofit screw-in LED "bulbs." Caveat emptor.

In real life, people and things illuminated by halogen MR16s look better than when illuminated by line-voltage halogen bulbs, which in turn look better than when non-halogen incandescents are used.

This is subjective, and not everyone will judge this to be the case. Check carefully before purchasing.