Sony home theater system

[JCarr2]

I've read pages and pages of posts, and I'm still a little confused. Hopefully I can ask the right questions to get to the bottom of my long search.

I have a very old home theater system (no DTS, no analog connections, no HDMI,) and I have a Sony blu-ray S301 player.

I need a new home theater system so that I can still get surround sound (right now, any DTS-HD tracks only come out of the front speakers.)

I DO want to buy a complete system instead of buying a separate receiver and speakers to keep things cheaper. I'm looking to spend around $400.

I've been looking at the Sony HT-SS2300, and I realize not many people are fans of Sony around here, but I just have a few questions.

By hooking up my blu-ray player to this system with an HDMI cable, will I be able to get surround sound, even if it isn't HD?

My player does decode Dolby True HD, so can I get that in HD out of this system?

If down the road I get a player that can decode DTS-HD, will I be able to listen to that in HD with this system?

Finally, I'm a little fuzzy on the whole passthrough thing. What exactly does it mean, and specifically in regards to this system? Will I never be able to get HD audio with this system?

Thanks for reading this, and I hope some of you will take the time to respond. I really appreciate it. I'm grasping at straws to try and figure all of this out. Salespeople seem to give me blank stares when I ask them these types of questions.