Rel Strata vs. HSU VTF-2

Has anyone compared these two models? What are the pro/cons? I am leaning toward the Rel but at more than twice the price, is it worth the extra money?
SInce HSU is a mail order outfit...hard to do an a/b unless you have a buddy or dealer who will loan you a REL...that being said...the reviews they have garnished have been very favorable...I assume they offer a trial period(most mail order outfits do)...that being said...RELs are awfully good subs...are there are not that many out there...good luck..
Thanks, I forgot to mention that this is for a 2-channel system.
They are both very nice subs. I would definitely give the nod to the REL; but keep in mind that a REL Stratus III cost $1300 for black, and $1500 for wood veneer. The VTF-2 is $495. So the REL should hopefully be better. If you want a new sub and you are on a budget, the VTF-2 is great!
Another option...Adire audio makes some highly reviewed subs as sales also...I believe it is the RAVA..or something close to that...around $4-500...check out their website..cheers
If you are considering Rel, also look at the ACI Titan II LE. Lost of people choose ACI over Rel including me. They are also mail order only thus the better value proposition.