You may wish to look at Totem Kin subwoofers. Their ultra-compact 8" sub sounds fantastic, is extremely well made, reasonably priced, and looks great too.
Inexpensive but decent 8" subwoofers
My current setup is Bluesound Powernode (N330) -> Blueroom Minipods
Which obviously isn't a high end system, but balances decent sound with sleek looks.
Looking for a 8" subwoofer which won't break the bank. Bonus points if it also looks good/minimal!