Well, I'll be the devil's advocate for this thread.
With the importance of wire (interconnects specifically) I think your budget would be spread pretty thin if you bought separates. I don't think you should so easily dismiss a good receiver (Marantz, Denon, Yamaha) and as money becomes available, buy a separate amp to use with your receiver (your receiver in effect becomes a preamp). I think the separates you will be able to afford with $2500 (not including wire) won't be dramatically better than a quality receiver, plus you stated you are more into HT than music; I don't feel you will get that much more umpf from separates just watching movies. Also consider that once you make an investment of that kind, you want to protect it with a decent surge suppressor / line conditioner that wont interfere with the dynamics of your gear. That will be at least a $500 purchase used.
Now start thinking about good interconnects and speaker wire to get the most out of your gear. That will run you another $500 on the used market.
I started out as you did, and I bought a decent integrated amp and then a separate amp for my mains (I was into HT as well). Now Ive dumped my HT gear and own complete separates, 2 channel only. Basically what I am trying to say is you are on a budget and cannot afford to buy EVERYTHING you need with seperates, so dont. Look at this as a long term hobby and upgrade yourself as money allows. With that mentality, take your $2500 initial buy-in and get everything you need to get your project off the ground: speaker wire ($300-400 for all 5 channels), interconnects (remember you will need AT LEAST 5 ICs to run your HT, $300-500), a good receiver ($1000) and a good line conditioner ($300-500). We havent even thought about power cords yet. All the prices I listed are assuming you buy used.
My plan gets you up and running with very good sound, and also allows you to upgrade yourself as you can.
m-