Looks a lot like my first set
HK 325
Fluance SX-HTB
Fluance SV-6
Dayton 10"
12 gauge from Fluance
I went with 7.1 originally but now I'm back at 5.1
I miss the immersion of 7.1 a little bit in some circumstances... but overall I'm much happier with my current speakers naturally
Addind a couple SX-HTB surrounds isn't a good idea at $100. The $120/pair SV-6s are nicer if you want to add a pair.
I'm not sure if I'd do 7.1 over 5.1 if I had to do it over again. If you have a really large room that's you're trying to fill it's a good idea, but if it's a pretty normal sized room it's not going to make a huge difference. I hadn't originally planned on it, but when I found out that my speakers were backordered and not going to ship for another month after my receiver and sub I felt the need to get some 2.1 action going until I could get the main speakers.
For your DVD player to your receiver you can use a digital coaxial cable or a digital optical cable.
These will work just fine.
If you want something a little sturdier (wont improve sound performance, just the cable itself will be of higher quality) you can get something like a dayton cable from partsexpress. I'm not sure what shipping is on either of these places for you.
Dayton 3'
Dayton 6'
You could also go with a digital coaxial cable. If you have a yellow 75ohm RCA cable around your house, that will work perfectly well.
Optical vs Coaxial shouldn't make any difference in sound.
For the sub you just need a single RCA cable. Run it from the subwoofer pre-out on your receiver to either the L or R RCA input on your sub. You can get a special subwoofer cable if you want. It will tend to be thicker and sturdier for putting under rugs etc.
Banana plugs are used to put on the end of speaker wire so it's easy to plug them in and out of binding posts.
If you don't have banana plugs or something similar, you're going to need to unscrew 20 connections every time you want to unattach or reattach your system (If you're only setting this up once and it's going to stay there, then it doesn't really matter since putting the banana plugs on was initially as much work as stripping and screwing in new wires was).
I've connected/disconnected my system 3 times since I got the banana plugs and I already consider them paid for.