Subwoofer Set Up

Bob and I totally disagree on this, he comes from a HT perspective while I am oriented toward audio. There are several subs that will work, I use REL and Hsu. The larger subs will overpower your room, I have a pair that use 4 12" a side in a large cabinet and I don't use them in my room which is similar to yours except being twice as long. Two 10" subs will give you all the bass you need in a room your size. Or one 10" or 12" if they are good quality. I would start with one better one and add a second later rather than start with 2 cheaper ones if that was the choice. There are several other powered subs that I have not used that have good reputations.

Bob and Stanwal, Thanks for response. I was thinking to go
with one REL B2, 10" and then to add another if necessary or I
should go with one B1, 12". I would really appreciate Yours
opinions.
Thanks

Two subs from the start. Check out Floyd Toole's comments on this area, in his book 'Sound Reproduction'

Check out the research on sub placement by Welti, Toole et all at Harman International. With two subs, try placing them at the mid points of each side wall as a starter. Also read Dr Floyd Toole's lastest book where he spends many pages considering placement for constructive and deconstructive interferance to help reduce peaks and raise nulls.