Yeah i agree, the custom work required to properly fit those 2 sets of ADs properly will send you broke. Youre much better off to fit an aftermarket head-unit and sub / box / amp package.
As an option, look at the Jaycar CS-2271, 12" subwoofer in its own ported box with a 200wrms amplifier built in. Nice and simple design which is fairly easy to install:
12" Active Subwoofer - Jaycar Electronics
RRP is $269, so add wiring ($50) which leaves you with around $180 for a decent head-unit (easily get USB/Ipod, MP3 etc for that).
Then just allow a weekend and you should be able to get it all fitted without too many dramas.....as always if you run into any troubles you can ask on here and someone will be able to help you ASAP.
I know you said you suck at DYI, but if you try to get a head-unit, amp and sub / box bought and installed youre almost certainly going to go over the $500 budget, probably closer to $600 for decent gear. By decent i dont mean the best, but something thats going to last several years and not start playing up and / or breaking within the first year or two.