DIY Sub vs Big Name Subs

Hi,
I have N802's and I have been thinking of integrating a sub into the system to augment the bass. They are awesome at punchy bass but not into the low regions.

Will a kit sub like VMPS or Northcreek be able to compete with say a B&W ASW 800 or REL Stadium?

I could get 2 diy subs to run in stereo for quite a bit less than a single "big name" sub.

Another problem with REL is that with monoblocks I am forced to buy 2 and I cannot afford that much.

System:
B&W N802s
Parasound JC1 Monoblocks
Cary SLP2002
MF A308CD

Thanks