Which sub to buy?

Hi all, can anyone suggest which sub would sound great with my MONITOR AUDIO BR5 speaker's. The reason why i did not buy the BRW-10 subwoofer that usually come's with the aforementioned speaker package is that after reading quite a few review's i concluded that it is not a very good sub at all, also i was short of money at that time and i am glad i was otherwise i would have bought it. But now i have a budget of around £400 but i might be able to stretch to around £500 but i do not really want to if possible. I therefore need some good advice for which sub's will sound, look and blend in nicely with my speaker's also more importantly which one's to avoid. So come on guy's and girl's which one's shall i consider and which one's shall i avoid. Sorry but i nearly forgot to mention that ideally it should be black in colour. Thank's.