my long lived Infiniti BU-120 seems to have finally given up.

Found the standby light off while cleaning up in preparation for a family dinner event, and opened it up to find a blown 1A fuse.

Replaced the 250V-1A fuse, plugged it back in (no music or nothing, just powering up).

Loud hum, unplugged, plugged back in, still a hum, and then the light died out.

Fuse blown again.

So...my other current parts:
Onkyo 705
Infiniti SM Center and Fronts
Infiniti Reference Two Sides
Energy RC-Mini Rear surround
Another Infiniti 12" Sub (post BU-120)

Easy buy for me is a replacement sub in the $300-400 range, but if I will get a good, solid product, with some impressive results, I would look up to $600.

Should I stick with the Energy line, and using the RC-Minis work up to replacing my fronts in the near future to match?
http://www.energy-speakers.com/v2/products/product-page.php?id=38#

Looking at the Klipsch RW-12D I kind of like the IR interface that I could program into my Harmony Remote.
http://www.klipsch.com/products/details/rw-12d.aspx

If $600 (shipping and all) is a firm cap you get tons of performance from the A5-350. Based on what others say it's really in a class worlds above anything you can get for less. I started with a budget in the $350-$400 range, but after reading here for a month or so I decided to stretch it to get the A5. If you're willing to spend a bit more for shipping the Epik Knight is $599 + shipping and would be comparable (and you'd get it faster.)

read some of the eD threads as well.

Called eD and they are 6 weeks out...

If you read through the subforum, you'll find a lot of respected ID subwoofer companies. Here's some pages to look through- all are well respected for price per performance:

www.svsound.com
www.hsuresearch.com
www.**********

I own two SVS subs (PB10 and SB12+), and am very happy with them. If the Infinity is the one I'm thinking of (BU-50's big brother), then any of these subs should beat it out in quality and headroom.