sub-woofer recommendation for 2.1 channel


I'm currently using Primare i21 integrated amp and Totem Model 1 Signature speakers.
Recently, I set up the speakers in Joachim's method (http://www.audiophysic.de/aufstellung/beispiel_e.html) and realized that bass is very weak. So I started to think about getting a sub-woofer that I can hook up to the Primare integrated amp.
Do you think it's a good idea to connect a sub-woofer to the 2-channel amp? If so, can you recommend an affordable one that can be a good match with the current system?
Thanks in advance.
henryjudy

03-15-12: Henryjudy
Thanks for your recommendations on the Martin Logan subwoofer.
However, I'm not sure how I can connect the ML subwoofer to the amp.

Please take a look at the pictures of the speaker and amp.

http://www.audiovideostore.com/images/MartinLogan_Dynamo500_front_02.jpg

http://big54.ru/published/publicdata/A229541/attachments/SC/products_pictures/Primare-I21%283%29_enl.jpg

You're all set for a good connection. Your Primare has a pair of pre-outs. That's preamp outputs tied into the selection and volume settings on the front panel. Connect a long pair of RCA plug interconnects from the Primare's PRE OUT jacks to the Martin Logan Line Level inputs, set the toggle switch to Crossover Variable (L&R In) so you can adjust crossover point and level settings and you're there. You'll have to experiment with placement and flipping the Phase switch for best integration.
A long time ago, I had the Primare A20 MKII (your amp's ancestor) with Dynaudio 52 monitors.

I used the REL Strata III sub via high level outputs; it blended very well.

I don't think you need to spend big bucks to get the benefit you're looking for. Certainly closer to $500 than $1000, put it that way. If I was buying again, I would think about a kit like this:

http://www.madisoundspeakerstore.com/subwoofer-speaker-kits/sb-acoustics-12-powered-subwoofer-kit/
Look into this sub from RSL.

http://rslspeakers.com/RSL_Speedwoofer_10.html

It is the sub I bought for my maggie 1.7's and the only one
I could get to blend with them. Now I sold the maggies and
have Martin Logan CLS. This sub should blend perfectly with your speakers, and if for some reason you don't like it, (I doubt that will happen) you can send it back for a full refund, they even pay return shipping! Also, it includes a
remote to let you adjust X-Over & volume from your listening
position. Another great feature at this price point!!