Ok - a few things. (am very familiar with Dynaudio Products)
1. If your Dyn's are new they will sound dreadful for quite a while - they will start to open up at about 200 hours and at around 500ish will be a different animal. You will stay with them for life until you can afford higher end Borresen's or Raidho's.
2. @kofibaffour - This is no longer correct (I am aware that this was the general wisdom a while back). I had my dealer call me in to listen to Temptations with a valve amp. I thought he was pulling my chain. They sounded amazing. Since the Dyn's thrive on current, a good tube amp will have loads of it.
3. you need a sub, or preferably two with those speakers. It will make the world of a difference. Two will open up the soundstage and give added depth.
4. Agree with lanx0003 - a soldered valve design is ridiculous. There is absolutely no need for that.
5. I now have my C4's and my Contour 3.4's on valve gear. They sound amazing.
Have done loads of A/B comparisons with Krell, Pass, ARC, Moon, Primaluna, and Don Sachs with both Contour 5.4 and Confidence C4. Surprisingly, the Don Sachs (at 27 watts) sounds the best with Primaluna a close second. (The Don Sachs Pre is the best sounding pre I have ever heard). Since I live in the UK, I cannot get Don Sachs here so I have all Primaluna gear in the UK. I have the Dialogue Premium HP Integrated (Evo 400 predecessor) on my Contour 3.4's. I have Dialogue Premium Pre and Dialogue 7 Monos on my C4's. They are both very good. The separate's are better than the integrated - but it costs almost 3x the price for about a 10% difference.
My advice would be get used separates if you can (I would buy used separates over new integrated) as this will be a little over your stated budget. Otherwise get an Evo 400 or Dialogue HP integrated. Primaluna are very easy to maintain and is the reason In went with them over Audio Research. Also, ARC gear has a colour, whereas the Primaluna is warm but almost solid state sounding. Primaluna are very easy on their Valves whereas ARC runs them ragged which is another reason why I went with Primaluna. ARC gear is also a pain in the arse to replace a blown valve.
6. Separates will have tonnes of current (double) for your Dyn's, and it is current that they love first, before watts.
FYI, I work in tech and have no affiliation with any audio manufacturer or retailer.
Good luck with whatever route you choose and remember to have fun with this along the way - and enjoy the music.