what can a stock 91 accord ex handle?

1991 honda accord ex As in, how big of an amp can I go before I need to upgrade things like wiring and alternator? Currently, I have a single 12" Type E alpine, and an Alpine V-power 350watt amp I believe. I cant remember exactly, but thats close. And a CDA 9851 alpine receiver. I wanted to go with a single 12" Type R sub with an MTX TA-4501 amp. The RMS of both are 500.   Now, does that mean the amp is 500 watt or is that the minimum it puts out? Cause the Subs peak is 1500watt. Assuming the amp is 500 watt max, does it mean the sub will barely run, or run fine? Sorry, im still a noob at car audio, it doesn't quite make sense to me yet.

In regards to the alternator, think about this way; Auto makers use an alternator that gets the job done for what the car requires and demands, but usually nothing more. However, you may not use every feature all at one time so the alternator is not always stressed to the max, but the addition of amp, almost always exceeds the output of the alternator. So technically there is no room for addition. BUT, the reality of it is, there are many factors to this situation. Take for example my car. I have had the stock alt. and a regular duty battery for years with no issues, with the exception of light dimming. I however don't necessarily play my system at full blast, all the time. So what does that mean for you? I would install it and see what happens, with the addition of the big three. As for your amp and sub question, disregard the max power ratings on the components (amp and sub). You are in the right direction in choosing an amp that produces xxx rms (continous)watts matched with a sub that handles xxx rms watts. Make sure it is a dvc 4 ohm sub in your situation.