subwoofer for music?

Hi all

My Speakers are the neat ultimatum mf5 which claims to have specs of

MF5 response @ +/-3dB is 28Hz - 40kHz. The typical - 6dB point in the bass is 22Hz. (from BOB of neat)

Can a 6.5" driver get that low?? Proacs and PMC also have specs that go that low! While speakers with drivers of 12" only gets to 30+hz usually...not sure why

I dont feel a lack of bass from the speakers, but having a sub that can fulfil both role of music/movies and help my system to get down to 20hz will be awesome! (will set the crossover at 35hz or less)

However i will have a subwoofer regardless because i will use it for theater, and the pv1d just does not cut it for movies. So therefore im looking for a sub to be used for music and movies with budget as low as possible.

Will 2 subs help stereo imaging? I would much prefer a single sub for convenience .
Room is 8m(6m usable) x4m. So after reading some info, here are some choices that is within my budget (but i would prefer to spend as little as possible)

-jl audio f113

-twin velodyne spl 1000 ultra

-jl audio f112

-bower wilkin db1

-velodyne dd15 (not plus version)

-twin jl audio f110

-mk 350 mk2

-rel r528

I heard about SVS and KK and paradigm subs, but they are a pain to get in my country

Any help will be appreciated. Thanks all :)