When looking at suits, you might want to consider checking out some made from "PBI" kevlar blends instead of just nomex.
PBI use to be exclusive to Pyrotech brand, but I believe you can get it from other manufaturers now. (even though most don't list it in their catalogs)
I have had two pyrotech PBI suits and have also worn nomex over the years. I had a brand new suit custom made last year (X-mas prez to myself) and it too is PBI.
If you spend much time in these things you want to be as comfortable as possible & the PBI wins hands down on comfort. (it is also a very good material)
The manufacturers have basically two gripes about the stuff.
#1 it is expensive to buy, so your suit will cost a little more.
#2 it takes special shears to cut the stuff, & it is only available in a cardboard tan looking color because it deosn't take to being dyed very well.
On my new suit, we got around this by putting a light layer of nomex on the "billboard" and epaulets of my suit.
Also, it is a good idea to have "pleats" made into the suit around your rib area so you can bend & flex easily in the suit.
You want to be able to move around in the thing without having the sleeves or legs pull up, leaving any skin exposed!
Oh, and make sure they use a fire resistant zipper!
One more thing, I cringe when I see guys at the track working on their cars while wearing their suits. If you get grease,
oil, etc on the thing, that is a bad BAD thing!