The Strip vs Fremont/Downtown
Is there a significant difference in quality? The Strip prices kill the wallet. Is it worth the splurge? Or are the Fremont/Downtown restaurants just as good?
Mon Ami Gabi in the Paris Hotel facing the fountains of the Bellagio will NOT "kill the wallet" While not the caliber of Prime or SW, the hangar steak with pomme frites is very good. Check the website for pricing.
As for downtown, look at Joe Vicari's Andiamo Italian Steakhouse at The D....new; but with an "old-Vegas" feeling and excellent service.
As mentioned above, the food downtown isn't anywhere near as refined, but it is magnitudes cheaper. If you want very good food (not comparable to best on the strip though) without breaking the wallet, there are plenty of places off strip that can meet expectations. If mobility is an issue, the Barrymore near Wynn/Encore is an excellent choice. You can get a decent steak on Paradise for considerably less than on the strip. Also check out Charlie Palmer's Cut of the Week. If the menu works for you, it's a steal. There are a few hidden gems (some on and some near the strip) that will probably serve you well at an acceptable price point. Depending on when you're planning to go has an impact as well. Lots of top notch strip restaurants offer an unpublicized/locals prix fix menu during the off season.