SSTR's used are still really pricey.The 4B ST is what I'd buy for front pair (just got one for a buddy wo has very revealing Maggie 3.6's and he loves it).They had big leap foward with redesigned transformer I belive (don't quote me there though).It is, for mains, most bang for buck.But be prepaired for $1250 at lowest and more like $1500.for a sub the 4B would work fine but you probably won't find one with any or at least m uch of the 20 year warranty.But it will be more like $750-800 and work just fine for a sub.As far as waranty goes don't sweat it.Like the old Crown DC 300's ( a venerable musician and PA amp) they are waaaaay overbuilt and should last 40+ years if well ventiallated and not abused.
Chazz
Chazz