There aren't too many inexpensive gourmet restaurants in Vegas. A bowl of tomato soup at Mesa Grill is $12 (but it's really good soup). If you're motivated to rent a car (which for a day can sometimes be cheaper than 2 taxi rides), and like Thai food, one of the best Thai restaurants in the country is in Vegas - check out Lotus of Siam & try the tempura as an appetizer and the Drunken Noodles (with chicken, which isn't on the menu, is $9 - with seafood, which is on the menu, much more).

Since you're not a gambler, depending on the weather & what time you get there, I'd definitely recommend doing the car, having a good lunch (assuming you get there in the day?), and maybe drive out to Valley of Fire (beautiful on a sunny day around 3-5pm in the winter as the sun goes down).

If that's not something you want to do, then I'd recommend either cabbing it to the Strip & walking the Strip and check out the installations at the Bellagio & wander down to the Venetian & check that out and maybe the Wynn as well. If it's after December 15, check out Cosmopolitan too. 8 hours on the Strip as a non-gambler is a long time - so if you're not all that interested in checking out casino's, then do the car rental thing.