You gave model numbers but not manufacturers. I have no idea what a Tarantula amp is. I know that Soundstream had a Tarantula line at one time. I think your subs may be Rockford Fosgate since they start with an RF. $100 per sub for sound quality? Not in my book. Also, your slot ported box. What's it tuned to? That's a big thing with ported subs. If you tune too high it will be boomy. Finally your EQ. Do you need it? You really shouldn't add an EQ until after your system is installed and tweaked. Then only add it as a last resort. Your will need to run something like
True RTA and look at your system's response and then tweak from there to get it flat.
How hard is it to install? Easy if you take your time. I've worked on a base Impala when I installed an XM receiver. It took 5 minutes to pull the factory radio. If you order your head unit from Crutchfield, they send you instructions on how to remove the HU as well as all of the speakers. Door panels are easy if you know where all of the screws are. When I used Crutchfield instruction to upgrade the front door speakers, it took an hour for the first door and 30 minutes for the 2nd. Amp installs are a little more difficult since you have to run wires from the battery. It's really a 2 person job.
Look around at other options. Like CDT and Elemental Designs for speakers. They have some high quality models. Or you can piece together some components from Dayton RS series mids with Vifa tweeters.
DIY Mobile Audio has some great advice on what works and you have very little of the juvenile chatter like on other car audio forums.
I'm not sure about prices but here's what I would do about speakers and subs:
1 ED 9.2 - 2 channel amp for your front speakers
1 ED 6500 - 6.5" component speakes for your fronts
(Leave your rear stock speaker and power then with the HU or don't connect them at all.)
1 ED 9.1 - mono amp for the sub(s)
Subs - pick one of the following that best fits your budget
2 ED Kv.2 12's - Good subs for the price but the are "budget" class
2 ED Ov.2 12's - An upgrade from the K series.
2 TC Sounds TC-1000 12's - I'm a TC Sounds nut. The 1000's are EXTREMELY clean sounding.
1 TC Sounds TC-2000 12 - An upgrade from the 1000. You only need a single sub.
2 TC Sounds OEM 10's - The same motor that is used on the 2000 but with a nomex fiber cone. Very nice.
All of these will work in sealed boxes. Don't go ported. You don't need it.
If you decide on TC Sounds, then act quickly because prices are going up in 2 weeks.
-Robert