^Yasmin, you bring up an exc point about new technologies "around the corner", but I don't consider 4K a factor at all-even once available it will actually matter only for really large displays. I suppose the question is if you want to upgrade now or just wait. In addition, we could talk about the rest of your gear-for ex., you have nice Kef speakers, but how many channels are you running and what about sub(s) (3.0, 5.1, 7.2, etc)? Also, we should take into account your goals-is it exc stereo and OK HT, exc HT, exc MC music?). For me, I was intent on improving overall SQ for my 7.2 DSX wides system and when I heard about the latest Audyssey breakthrough, I knew it was just a matter of time before I'd have it. And I'm glad I didn't wait for whatever next year may bring as I'm really enjoying it now.
As to separates (and keeping in mind I'd not use my 4310 as the amp), is there an advantage, the idea being to change out the pre/pro for the next model? Not by me. I've found the real bargains in high SQ HT to be certain carefully chosen AVRs, like the Denon 2808, 2809, 4310 and 4311. Especially as I've found reselling those choice models is easy if done while they're still fairly current models. This is a good time to sell a 4310. Also keep in mind it's far easier to resell an AVR than a pre/pro. And doesn't the higher pricing in Europe translate into higher resale used?
The situation in Europe is different in that you can get the SC5509; we cannot in the US, but I don't see that model as having any real significant advantage over the 5508 at all. The Integra versions are the same models but are simply more expensive so I'd just skip them. My criteria was that to be worth relacing the impressive 4310, the new model would have to have XT32 and be Audyssey Pro capable. That leaves out the Onk AVRs (they're not Pro). I strongly
considered the 5508 and I was a bit queasy because of a couple things. Some units had some kind of wiring connection issue requiring going into the shop and all the Onkyo/Integ models run quite hot. If you are considering getting one I'd just go to the thread and ask specific questions as to problem risks and for sure plan on getting a fan. The 4311 is problem-free and runs cool (other than some folks having minor occasional fussiness/glitches getting the Web Control Save feature to work) .
As to my decision, I'd gotten an Emotiva XPA5 because my 4310 couldn't drive my Dali Helicon 400s to reference (though my 4311/A100 can!). So I didn't need to buy an amp for 5.2 but if I was to keep the DSX wides I'd need to buy another 2 ch amp if I went with a pre/pro so that effectively added hundreds to the price of a 5508-which here was about the same price as a 4311. In addition, other factors tilted me to the 4311. Denon has the Web Control feature allowing you to save and reload calibrations which I like and has DenonLink for use with a Denon player which has turned out to improve my music SQ off shiny discs. So I'm quite pleased with Denon. Not important for me, but the 4311 is 11.2 capable, the Onk/Int are only 9.2.