Questions re: DIY TV/Hifi Cabinet with built in speakers

HI,

I am currently building a Hifi/TV cabinet to house a home cinema pc, Kenwood KRFV5050 av amp, cable box & vcr, and I want to build in the front left & right speakers & the centre speaker. I am limited with size of speakers, in particular the height, so I'm having to stick with bookshelf ones.

The speakers I'm looking at using are Celestion F1's as the fronts (& rears) and a Celestion F Centre. The reasons for this are more down to size & price than anything else.

I intend building an open box around each the speakers, with a gap of 5mm between the sides & top, and the speakers, with the intention of using some sort of fibre in the gap to let the speakers float isolated from the cabinet. The front & back will be open and I'll cover the front over with speaker cloth.

I have a few questions....

Is there a cheapish subwoofer which would compliment this system?
Anyone suggest a material for the gaps?
Anyone any better ideas of how to incorporate the speakers into a unit?
Whats this lot likely to sound like?

ANy help much appreciated.

Cheers, Martin.