I'd recommend taking a long hard look at the 6.5x55 Swede. I was in a similar situation as you several years ago and after considerable research and deliberation, I decided on the Swede for several reasons. I'm not a high velocity guy and I'm not a magnum guy - I really see no need for them. I like classic cartridges and I know I'm not the first to say it, but the grand old classic cartridges are still around and are still going strong for a reason - they work and they work well. Additionally, the 6.5 SE has very high sectional density, and is a fine long range caliber if loaded to its potential. The real world performance is far beyond what the ballistics might suggest as well, and as I'm sure you're aware, the 6.5 is considered a fine moose caliber in Europe. The mild mannered Swede is easy to shoot accurately and there are some great rifles on the market to choose from. I also believe that the 6.5 SE will be around for many, many more years, while some of the "new-fangled" cartridges will have come and gone. Bottom line: choose what meets your criteria and don't look back. The truth is, you really can't go wrong with any of these choices. Find a rifle you like and choose your caliber based on what's available in that particular rifle. Since I prefer CRF/Mauser actions I went with a CZ 550 (6.5 SE) and I am very pleased with both the rifle and it's performance and these rifles can still be found on the secondary market for very reasonable prices.
Never owned 6.5mm rifles save 2 Swedes. A M70 FWT and now a Howa 1500. I am very impressed with the caliber and how easy it is to find accurate, high velocity(relatively speaking) loads for same. I'm a believer.
