Sub Question
 

I have a 2006 Accord EX. I was wondering if it was possible to run an 8" sub in the trunk with the stock head unit. Will it sound crappy?

I'm quite familiar with the Inifinity Basslink and their relatively large price tag for amount of bass.

Is it possible to run an amp solely for a sub without getting a new head unit?

Thanks

RE: Sub Question
 

Yes, yes, and yes.

Yes you can run a sub without an amp (with in-line cross-overs).
Yes it will sound crappy and degrade the sound of your entire system, likely resulting in less bass than you have now.
Yes it is possible to run an amp soley for the (trunk mounted) sub w/o replacing the OEM Head Unit. You tap into the rear speaker wires and get an amp that accepts in-line (speaker level) inputs. There you go! You'll have to wire the amp (power/ground/remote), but the install should be clean/simple.

However, if you're going that far, you may as well run extra power to all the speakers via a nice 4 channel amp... You'll have to run an extra set of speaker wires from the head unit to the rear as outputs (use two channels as right and left signal). Cut the speaker wires at the HU and splice the two sets of wires to the front right and left speaker wires. Ah heck, this is too hard to explain in a post... well, just go to many online car-audio websites for wiring suggestions. Just trust me, if you're buying and installing an amp and sub, it's not too much extra work to hook into the factory speakers to power them as well... The stock 120w system likely only sends 10-12w rms to each speaker... Any added clean wattage would see significant results. You'd be running the left and right signal of two channels of the four channel amp. You would lose fade (no biggie), but keep balance and stereo. The remaining two channels could be bridged into a much higher wattage output for the sub. This is typical use for a 4 ch amp and gets a great use of it power. For instance, a 200 watt rms amp (50w x 4) running in the above config. should see each of the four surround speakers getting 50w and the sub getting 200w. Ohms law or some such, lol.

Best of luck, lest us know how it goes.

RE: Sub Question
 

Thanks for the valuable info Trihonda. I'll update if I do anything major.