Add Integra to jonnjbarlows list - they are the upscale brand for Onkyo.
Am not familiar with your amp - I did a quick google and its unclear to me what you would do with 12 channels of audio.
So two ways to look at:
1) Buy a preamp processor - let's use the Integra 9.8 as an example since I own one. They have been showing up for under a grand here. This has the feature set you are looking for so you can compare anything else that strikes your fancy to it - newer gear will have a few more Audyssey features but supports the same standard. Plug it in to your amp. When you want better sound, get a new amp (or any number of spectacular used ones here).
The long term view here is that in some number of years (at least five IMHO) new gotta have standards and formats will emerge - at that point you jettison the pre/pro but you keep the amp and the speakers - technology which basically stays the same and will continue to sound as good or bad as it does now
OR
Buy a receiver with all the features of the Integra - again Denon, Marantz, Integra, Onkyo, NAD and a few others. One easy way to research this is to go to the Audyssey website - they list all the gear licensed with their MultiEQ technology.
(In case you have not read my other posts, Audyssey is a profound change - as significant as HDMI 1.3, with a much greater impact on your enjoyment.)
Anyhow now you buy the receiver. A/B the preamp outputs from the receiver to your current amp, and compare it to the sound of the receiver. Use the winner.
Later if you want to upgrade the sound get a better amp and just use the receiver as a pre/pro.
Since I am of the belief that you get what you pay for, I chose to buy a dedicated pre/pro. I couldn't believe that I could pay less for a receiver and get better sound. And there are lots of good arguments to be made for separating the amp and the pre/pro anyway.
All that said the Japanese have a unique tradition of building these wildly complex receivers and making them sound good.
If the money or the space matters it probably makes the most sense to buy the highest powered, feature laden unit you can find.
One last tip. Go to the various sites and download the owners manuals. Compare what is actually involved in setting up a few functions. See if you like the interface better on one brand then the others. Buy that one - ease of use is huge with devices that are as complex and capable as these.