Helping a Semi-Noob Purchase/Set Up the Right System

Hi there. I want to first say that while I am new to home theater systems, I have been doing my own research on the basics and have tried to answer as many questions as I could. The stickied thread (not allowed to post link, but "Setting up your home theater audio 101" is what I am referring to) was immensely helpful, but of course the more questions that are answered the more that are created as well.


But to the point of my post: I have been slowly building my home theater system, and all I have left to do is the Surround Sound, and I am looking to get some help from those more experienced as to what system would fit my needs well. If it helps, I currently have a Sony Bravia KDL-32M400 (HDTV), and a Samsung BD-P3600 (Blu-Ray player). I do not have a preference of 5.1 or 7.1 surround sound, I simply want to get the best bang for my buck within my budget (about $500, give or take $100), whatever that system may be.


In order to know what system would fit me best, I should tell you what I am looking for. I want a system that sounds great, whether I am playing video games, listening to music, or watching a movie. My blu-ray player can decode Dolby TrueHD and DTS-HD Master Audio, so the sound system does not need to do that. My Blu-Ray also streams Pandora, so I will be listening to music from that, and I also want to be able to listen to music from an mp3 player (not limited to ipods). My TV has a 'mini'-in input, and then a digital audio out (optical), so I believe this can be achieved even if the receiver I purchase does not support this. Lastly, I play video games, and have lots of old nintendo systems (using the standard red/white for audio), a wii, and an xbox (with hi-def avpack, meaning digital (optical) audio out) and xbox360. For the older systems, will the sound be ok to plug in the normal RCA to my TV, and then run a digital out from my TV to a receiver? Or is it possible to put the RCA inputs to the receiver, and then run the video to the TV (using HDMI?)? Basically, I am asking which is better: to run all A/V to the TV and then to the Audio Receiver, or vice-versa?


Now that what I am looking for is understood, I want to propose the system I found and have been heavily considering: the Onkyo HT-S5200 HTIB. It currently is 15% off on Amazon, new (meaning still has warranty) with free shipping. So it seemed like a pretty good deal to me...Although, it is important to note the TX-SR307, TX-SR507, and TX-SR607 receivers are also under the same deal (15% off, free shipping). If I only got the receiver, I was looking at Energy 5.1 Take Classic as the speaker system to get for them.


Does anyone have any opinions on the above systems, and which would be a better choice for me? Or are none a good choice? None are THX-certified, but neither is my Blu-Ray player -- does this mean it wouldn't make a difference whether or not the receiver was THX-certified? I have read many pages about THX-certification, and while I understand what it is, I am a bit confused by its implementation in systems -- is it important to get a receiver that is THX certified? If so, what is recommended? I've also heard some say Monster cables make systems w/o THX certification have such...but I didn't understand this, and I've never been a fan of overpriced Monster cables. Also note I currently do not think I will need Zone 2 or pre-out capabilities, but if they're there, great.


Lastly, I am a bit confused by what cabling to get. Are digital (optical, TOSLINK) cables the same audio as that carried by HDMI (except HDMI obviously also carried video)? Or is one Bit Stream output and the other decoded? Or is that simply a setting within the Blu Ray player? I am a bit confused by cables in general, thanks to a lot of supposed "high quality" HDMI cable hype -- is any of this legit? If someone could point out what HDMI cables are acceptable (or if all are) it would be of much help. Same goes for speaker cables (I heard 16 guage was the way to go?), and digital (optical, TOSLINK) cables (have not heard of any differences between cables).


Thank you VERY MUCH for taking the time to read this and help me out, as much of the information online is informative but confusing at the same time.


Edit: So I think I may have posted this in the wrong forum...it is sort of a cross between asking about set up and simply what HTIB to get (which belongs in the HTIB forum). I'm sorry, I do not know this site well, so if there are mods they can consider moving it (rather than double posting there).


Edit2: I think I may have finally answered all my own questions, and am now deciding between the Onkyo 6100 and 5200.