It would be like buying an SS - yes. However, it's at a lower price - with the new endbell and sintered motor installed - they'll perform like the SS for $40. It's effectively a "new" motor for half the retail cost of an SS.
Looking at the web site - however, it looks like a RMF EX 8.5 isn't there. They have 10.5 and 13.5 which have the upgrades. You know, the best bet may be the SS 8.5 over the Ex because of the higher Kv rating.
New SS 8.5: $79
RMF SS 8.5: $55 (which is a good option too)
RMF Vel 7.5: $40 (would be good for Mod Buggy)
RMF Ex 10.5: $40 (on a smaller, twisty track, would be fine)