@LankySwag ;
1) You can test the power wires (yellow and black wires usually) with a digital multimeter. That is the first thing you should get for a do it yourself install with subs/amps.
Set the multimeter for direct current and see if there is 12V+ going to the deck.
2) Consider including a custom box in your budget. I use starr mountain exclusively, but pro-rabbit is another good choice.
3) I love knu for all power/rca/speaker wire connections:
Amp Installation Kits
Use at least 14 gauge speaker wire (12 is even better...) for your subs. Some people use as low as 16, but I don't recommend it.
They have a GREAT amp connection kit for 60$ (250 amp rated 1/0 gauge)
4) Getting a great deck is well worth the money. If you buy used on the subs/amps and deck you should be able to make your budget go a lot farther. Increasing your budget by 100-200$ would be more ideal IMO, but you should be able to make $500 cut the cheese.
5) Here is my pick for a good starting amp...
F/S: Modded Image Dynamics IDQ1200.1 - DIYMA Car Audio Forum
Really clean power for your subs.
6) I would get a pair of 12'' 4ohm dual voice coil subs and wire them at 1 ohm on that amp, you will have a great system. Make sure you get a ported enclosure if you want to get louder. A good box builder will make an awesome sounding box that can also get loud. Tuned to 32hz or lower if your want sound quality... higher than that if you want to get really loud.
Best of luck.