I'm thinking about getting a Klipsch 120 THX Ultra sub. I'm wondering how this would match up against stuff like the MFW-15 or the A5-350.

Also does the Klipsch sub need it's own separate amp would I be able to hook it up straight to my Onkyo 805?

You will need to use a separate amplifier.

ID subs will definately be a more cost effective solution. The klipsch thx subs dig deep and are pretty loud though. But I'm sure SVS would outperform them, especially if you only want one sub, not duals.

It needs alot more power than your receiver. These like at least 500 watts. They are very nice subs and whether they compete Depends on the price you get it for. I would not spend retail, maybe half of retail. For an example my dual SVS 16-46 cs+ subs were very close but give the nod to the SVS subs. The ultra 2's were better than 1 SVS PB12/plus/2 sub. The klipsch sub system I had retailed for $3600 or so and the SVS duals cost me $1500 with my own amp added. I bought the Klipsch for $1800 with their amp. I would take the dual SVS's. They are very close though and many would pick either for the same price.

Lets say I can get it new for less than either of those two ID subs I mentioned.

Would it be worth it to get the sub and amp separately then? Also could someone rec me an amp?

How much less and factor in an amp. I have not heard either one of those, I do have eD's 18 inch driver now and like it alot. Tough call. The amp of choice would be the Behringer ep-2500. Alot of power for a great price.

I do know that dual klipsch THX subs would rock your world. Also, what size room? The Behringer is 2 channels and would love 2 klipsch subs.

I could get the Klipsch for $500. I see the Behringer would put me back about $300. My room is 20 ft by 15ft by 9 ft.

I could get the Klipsch for $500. I see the Behringer would put me back about $300. My room is 20 ft by 15ft by 9 ft.

Thats not too bad of a price, if possible try to pick up two though :D

I do know that dual klipsch THX subs would rock your world. Also, what size room? The Behringer is 2 channels and would love 2 klipsch subs.

just to throw in a heads up, make sure what ever amp you get has the Speakon® NL2 connectors. I'm not 100% sure the 120's have bananna jacks on the back.

Is this really the best sub I could get for $800?

I'm including the amp because I wouldn't need one for the others.

If you have good room gain the eD A7s-450 will be better. This sub will dig down to 22 hz but good room gain will make it extend very low since it is sealed. My DIY sealed eD 18 inch subs will rolloff at 18 hz(bigger enclosure than the A7s) but in my room extend down to 5 hz. The eD will be much better from 22hz and up without room gain. Also much more powerful.