Klipsch RW-12D Subwoofer: Repair or Replace???

Several options. Which one is best depends on your budget and system goals. Short term cheap, fix the amp again. Shop might make you a deal since they did the work once and declared it bullet-proof. Worth a shot.

A more upgrade option, if the speaker itself is okay, get something like the Dayton SA1000 to power it. For $400 you will have more power and lots of flexibility with adjustable phase and level, and even a parametric equalizer (one band, but still...) and the big advantage with this option is it sets you up for....

The best long term solution for really good low bass is a distributed bass array of 4 subs. The beauty of this is you start with the Klipsch sub and Dayton amp, then upgrade by adding additional subs. The low quality of the Klipsch will matter less and less as you add subs. Improvements each step of the way will be obvious, and if you get to four you will be amazed to find you have the best bass you ever heard, including systems much bigger/more expensive.

I started out with a couple of Klipsch subs, including the RW-12D.  I hate to say something is "junk", but in this case...  I never had any problems with mine, but in comparison to subs from SVS, HSU, Rythmik, and PSA, it really does sound like junk.  All it does it make some bass noises, not music.

I own the baby brother RW-10D and it had performed flawlessly since 2006.  With that said, not a huge amount of performance and has been in use in my small bedroom HT system for the last 12 years.  The RW-12D has a bit more output and grunt but IMO, like the RW-10D, not the most musical sub you could buy.  If my RW dies, I will go another route.

Maybe a similar size SVS or HSU would be good choices for you to consider.

Bill