INTRO:
First of all I am "NOT" audiophile by any means, I just wanted a setup that is a step above than my current one: Logitech Z-2300 with only the (L) speaker working (Right Speaker is dead and so is the Right port). I am on a strict budget, by the way.

Budget: "Embarrassingly Cheap to close to being free as possible"

What I "currently" have:
1. Creative Sound Blaster X-Fi Titanium HD 24-bit 96KHz PCI Express x1 Interface Sound Card powered by THX TruStudio Pro

What I am getting, budget permitting:
1. Subwoofer: (Currently on Sale @PCParts, so it's a no brainer and I am "NOT" an audiophile)
1st Choice: Dayton SUB-120 12" 150 Watt Powered Subwoofer
2nd Choice: Dayton SUB-100 10" 125 Watt Powered Subwoofer
3rd Choice: Dayton Audio SUB-80 8" 80 Watt Powered Subwoofer

2. Bookshelf Speakers:
1st Choice: Dayton Audio B652 6-1/2" 2-Way Bookshelf Speaker Pair
Mulling Over (I can dream can I?): BIC Venturi DV62si Bl 6-1/2" 2-Way Bookshelf Speaker Pair

3. Amplifier: (I for one cannot really tell whether I still need an amplifier with the above two but, then again I don't know jack about these stuff.)
1st Choice: Dayton Audio DTA-100a Class-T Digital Amplifier 50 WPC
2nd Choice: Dayton Audio DTA-1 Class T Digital AC/DC Amplifier 15 WPC
3rd Choice: Lepai Tripath TA2020 Class-T Hi-Fi Audio Amp w/Power Supply

Questions:
1. For a Mid-Fi/decent 2.1 setup (40% Movies / 40% Music / 20% Gaming), how do I set this up? how do I connect one to each other and ultimately to my sound card? What cables do I need to acquire to connect them and get all of them working together?

2. I have a lingering feeling that the Dayton Sub-120 will be overkill for a 2.1 system, don't you think? With this should I get it's younger subs: the sub-100 or sub-80 for that matter?

3. Do I still need an amplifier to go with my choice of sub and bookshelf speakers? If yes, then how do I get it connected to both?

Being a total dunce in basically everything, particularly in this audio setup project, are my choices for a 2.1 system sound/ok?

Thank you in advance!