I didn't do too much math to see if the bundled SVS speaker systems offer any additional savings over the a la carte pricing. I did see the 2 Ultra systems discounted only $200. If it makes sense and helps out in the short term, match up your Front three as Ultras now, buy the surrounds as Primes (350 gloss blk as opposed to 1K for the pair). You can still upgrade to the Ultra surrounds later, and move those Primes to Wide or Height channel.
Just a suggestion. Personally, if it came between the subwoofer or the matching speaker set, I would go for the sub early in the game. Check out the audioholic reviews:
SVS PB2000 and
Hsu VTF2 Mk5. The Hsu, delivered is $607 I think?
Best!