The topmount stainless sink won't fit closely to the back of the stone at the bowl edge. The caulk line can be huge.
Overhanging the bowl opening will help, but personally, I wouldn't want it. I r&r bad sink caulk all the time, and what ends up trapped behind a big caulk joint becomes really nasty and unsanitary. Sink caulk needs service every so often - it's never permanent.
A thinner gap, starting with clean dry surfaces, filled with high quality 100% mildew resistant silicone, lasts the longest.
Some sinks are better than others for moving from topmount to undermount. Mostly, they're unacceptable. My advice is to make sure you understand how fat the caulk gap will be, and how it will appear, before you make a final choice.
You can put a level, or a straight piece of 2x4 across the rim, and check the clearances, but that's really an inadequate visual check for a final approval. It's only good as an initial check, to see what you're getting into.
To really know how this will look, you can do a mockup from a nice flat piece of plywood. This way, you can model different overhang scenarios, too.
As to the price, there are lots of cheap ss undermount sinks available. To my way of thinking, there's no reason to go to the trouble of undermounting a topmount unit when perfectly reasonably priced alternatives are readily available from most fabricators and discount plumbing supply shops.
Just check out the referrals b4 you buy.
Regards.
