Which Batteries?

I'm currently bidding on some Dewalt packs(for 6S3P) on Ebay ATM but if I don't get them, which 5000mAh+ pack would you guys recommend i have room for 2S+3S or 3S+3S with 5000mAh+ cells (or 3 lower mAh 5S/6S packs in parallel).
P.S. I would like to keep the battery price(s) under $400USD

And regarding the motor I just wanted something fun and overkill...the LST I'll be using it in is far from stock, as far as drivetrain everthing but the tranny and axles has been upgraded (ie - diffs=tini+nova cups+gpm cases spur/pinion=tini) and the rest of the truck has been upgraded also using titanium and aluminum where needed, I'll post pics when it's closer to being done.