Well I would go with the AR15 and put a suppressor on that. On a tactical rifle like that a suppressor would be quite a useful addition IMHO. Plus it is a useful platform for other calibres.

IF you are interested in the option I mentioned of perhaps selling the two .17 HRM's you have and getting one that does have both a good trigger and a good barrel I did a bit of research among the makes I have had and can vouch for...if you check out www.sako.fi and look at the Sako Quad with the heavy barrel you will see that you can get one rifle which can take interchangeable barrels and magazines for all Rimfire cartridges and that the trigger is the same one you get on Sako centrefire rifles which is much better than those on most Rimfire rifles PLUS...you can order one with their two stage set trigger which you can "set" for a benchrest level of light crisp let off....

This system is exactly what I have on my Sauer 202 Take Down...a two stage set trigger option...and I have two barrels and bolts and mags...one in 6.5 x 55 which is fitted to take a suppressor...and the other calibre is .375 H&H for Africa and "other" long range use as it can shoot the same VLD bullets that the Cheytac uses by Sierra and the advantage is that it strips down to fit in an attache case which can fit in a rucksack without making it obvious you are carrying a rifle. The "set" trigger option is by far a worth while "option" if you like light benchrest type triggers which I do like as I use them in competition use all the time.

Having a Sako Quad in .22LR and in .17HMR in the heavy barrel versions so I only need the expense of "one" telescopic sight ( which are a high end expense )would be the way I would go....rather than have say "3" rifles each with it's own telescopic sight...( 2 x .17HMR's and I assume at least one .22LR ?) and this option ought to be "cheaper" in the long run.

Rifles with interchangeable barrels were said to be a "less" accurate route than a fixed barrel option but my experience of centrefire take down rifles in my Sauer is that if you can re-load them out to the "lands" they are every bit as accurate as any other stalking rifle and better than most if used with the "set" hair trigger. I shoot mine using 3 shot groups to evaluate the "stalking" profile barrel and both can deliver single hole groups.

My Sako 75 .243 could shoot benchrest 5 shot "screamer" groups...I sold that rifle with the load development and RCB match dies and the moderator and scope as a package and made a fair bit of money on it. Infact that is what I do to subsidise my shooting...I put together rifles and accurise them...then offer them for sale with some "coaching" so the shooter can match the groups the rifle can deliver...and I have never had a Sako or a Tikka which has not proven to be able to do this...and I have had six of them so far. Sako and Tikka share the same barrels.

I have not had a Quad though...and using rimfire factory ammo which you cannot re-load and "accurise" might make a difference...but in their heavy barrelled version I would put money on being able to get a factory load able to group well below sub minute of angle. As a plus I think you can also order the barrels pre- screw threaded for a moderator...so all told that rifle looks a good option to me. Infact I may get one myself.