The Acurus Amfitheater was a considered a "cutting edge" A/V Receiver a few years back, and I think it would serve as a good receiver for your home theater system today. I think that Acurus also produced an "AC-3" decoder a few years ago. I don't know if that decoder is still in production or not. I would click onto the "manufacturer's links" here at Audiogon and try to find Acurus from that. From there, I would go onto their site and try to locate thier AC-3 decoder then. If it turns out that their AC-3 decoder is no longer in production, then I am sure you can get a used one somewhere (either here at Audiogon, or at another website like "Audio Shopper" or "Ebay" (after all, that's how I put half of my audio system together last year. And I bought both of my VCR's off that site too. Man, I love myself some "Ebay", don't I)). Try doing those things first. You just might strike gold when you do. You never know until you try, right?? However, on the other hand, if you prefer to junk your Acurus Amfitheater A/V Receiver (which is something I wouldn't do) and you prefer to buy a brand new A/V Receiver, then I would look at the Onkyo TX-DS686 for around $800.00, or for a few dollars more (okay, let's try about $200.00 more), then there is the Yamaha 1000 (forgot the letter prefix leading up to the model number..... but I'm sure the others here on this board know which model I am talking about), or just like you said, I would look at a 2 year old Pioneer Elite model (that is, the one that was a $2,000.00 model two years ago) too, if I was going to go the used route. I think that's about it as far as receivers are concerned. But the first option I would explore first would be for you to hang on to your Acurus Amfitheater and hunt for an "AC-3" decoder that is reasonably priced.
Now, as for DVD Players?? How much do you want to spend?? Around $400.00?? Over $400.00?? Under $1,000.00?? What do you want the player to do?? Do you want to play music as well as movies?? Do you want progressive scan, etc.???? Some players under suggestion here include the new Toshiba SD-4700 (progressive scan...... for UNDER $400.00!!!!), the Onkyo DV-S535 is also another good choice (great picture, great sound, great feature set, well built chassis, but NO progressive scan..... for around $400.00 to $450.00), the Sony DVP-S7700 (around $500.00, from Crutchfield..... a little long in the tooth as far as technology is concerned...... no progressive scan, but still a solid player nonetheless), and for a little more money (say, $600.00 to $700.00), the Pioneer Elite DV-37 (progressive scan just like the Toshiba SD-4700, but with a more extensive feature set and a better transport and chassis....... sexy looks...... makes a good CD Player too).
And then for speakers, I would go with B&W DM602 MkII for around $600.00 a pair. The matching center channel should be available for around $350.00 to $450.00. And then I would go with a pair of B&W DM601's as surrounds, for just $400.00 for the pair. For subs, I like Sugarbrie's suggestion about the HSU subs. They make some REALLY nice subs for a reasonable price. $500.00 for a passive sub, $700.00 (I believe) for an amplified one. Otherwise, try the REL Q100E for $900.00. Also, there are subs from the likes of PSB, Paradigm and Energy for you to consider. They are reasonably priced as well.
And lastly, let's not forget the cables. For your system, I will suggest Monster Cable. I would also look into getting cable from the likes of Cardas and Kimber Kable.
There, this should help you out and keep you busy for a while.
Good luck, and let us know what you decide to eventually go with.