Budget subwoofer that matches Monitor Audio RS1?

Hi Dear Audiogoners,
I just both a pair of Monitor Audio RS1 and a Virtue Audio 2 integrated amp (really nice combo, BTW). Now, I'd like to add a sub to my system. I am looking for a used small (8-inch), budget sub (300-400) that matches the RS1.

My room is 13x15x11 feet. I've seen the Energy ESW-V8 for ~$300 (8" and goes down to 26Hz) Has anybody listened to this sub? is it good? Would it match my RS1 well?

Any other suggestions? I actually clueless about subs, since I've never owned one. So, any suggestion will be welcomed!!!
Thanks in advance!!

i still use an energy es-8 in my office system and it does its job well--musical, unobtrusive and clean, without the boominess of lesser products. they're very inexpensive ($100-150) used. however, if i wanted to step up, i'd get a hsu stf (around $300 on hsu's website)--tight, authoritiative and a fantastic value.
The Mirage Omni S8 is a very nice 8" sub, from the same parent company as Energy. I found it easier to integrate than the very well regarded HSU I had before. New price is around $350 but I bought one on ebay for $55 with 'cosmetic damage.' Turns out the damage was just tape residue that came off with some WD-40. It has both line and high-level inputs, phase switch, down-firing port. I'm very happy with it.
Look for a used Klipsch RW8 or RW10 subs with the Cerametalic driver - very fast and not at all boomy. Can be had for well within your budget.
Thanks a lot for the suggestions guys!! They all sound good and are on my list of "potential subs" right now. I will be looking around for more options for a while and then decide.
So, any extra recommendations will still be welcomed!

I picked up one of the Martin Logan Dynamos (original sealed model, (not one of the newer 500,700,1000 models which seem worse to me) last week at Magnolia/Best Buy for $350 on closeout NIB sealed.

Took a look at the floormodel as well for $280 but it appeared to have had a hard life.

It is a KILLER sub that is rated down to 25hz but I am getting 20hz almost flat in my room which is digitally corrected.
Elemental Designs A3S-250 for $350 new. Sealed box, low Q, 25 Hz, very good budget sub for music.