You know, some of today's home theater receivers come within shouting distance of budget-priced "audiophile" integrated amps. With that in mind:
(1) Pioneer's receivers in particular can sound very good. Your receiver is probably fine. Keep it until you can afford something much, much more expensive. In fact, try to borrow whatever you plan to replace it with to make sure it's really an improvement that's worth the money.
(2) As for the SACD player, there are so few discs out there these days and the difference between regular CDs and SACDs will be so slight as to go unnoticed in a system like yours. Save your money and use it for #3 below.
(3) The built-in phono stage and the stock cartridge that came with your Denon turntable leave a lot to be desired. Buy an outboard phono stage in the $100 range like the Cambridge Audio 540P, NAD PP2, Music Hall Phono Pack, Pro-ject Phono Box or similar and upgrade the cartridge to something like the $99 Ortofon 2M Red or Denon's own DL-110 for $140. You will hear a major difference now and even more so if you later use it in a dedicated two-channel system.
(4) Your receiver probably has decent DACs. Try feeding the signal from your digital sources into its optical or coaxial digital inputs. That may yield a nice improvement.
(5) Your speaker wire is fine for now. Wire is the finishing touch. When you get a system that you're happy with, THEN think about upgrading your speaker wire and interconnects.
(6) Finally, there's no reason why your home theater and 2-channel rigs can't coexist. Many integrated amps have home theater pass-through circuits so you can use your "audiophile" integrated amp for 2-channel and your HT receiver for movies without ever swapping a cable. Also, there are many "audiophile" home theater receivers available from the likes of NAD, Rotel, Cambridge Audio, Arcam, and so on. Don't count them out.
And don't listen to people who tell you stuff like "put your Playstation 3 on a $500 isolation platform" or "upgrade the power cord on your $300 receiver to a $1000 wire" or "replace your 14-gauge wire with $500 Fire Breathing Dragon Super Speaker Cable and it will make your system sound three times as expensive."
Just be sensible and enjoy. What you have now is not bad at all.
