for just good clean bass to add to yoru system get the type x. for an overall SQL budget setup get the Rs they will be quite a bit louder than a single type x.
yes, possible 135-140 when done right. dpenends really on what you think is loud. for my own tastes i would do 2 12 Rs but if i put it in my dads car i would do 1 12 x.
type x is an sq driver and sounds like crap in ported boxes.. so the type r's will get louder because there suited more for ported enclosures. of course u can still use type x's in ported enclosures you will just lose sq