Another thought is to see if you can install an "offset flange" to convert the 10" rough-in to a standard 12" location. it may not be wise structurally if it will require removal of much wood from a joist.

As to grades, the cheapest toilets generally don't flush well. A notch or two above that usually gets one that does. Beyond that it's esthetics as none of the expensive toilets are inherently bad, though I'd avoid all that require non-standard replacement parts- especially the fill valve and tank-to-bowl gasket. Prices will vary based on location, but here in upstate SC your quote is pretty high. Always get at least 3 quotes on any work being contemplated and be sure all are quoting the same methods and materials.

Phil