So you are planning on buying another 15-22 with integral suppressor (over $1000, not including stamp) as opposed to just a can... simply because you don't want to buy subsonic ammo? And by doing so, not have the opportunity to share the suppressor between other rimfires?
Do you realize how much subsonic ammo you could buy for what you are gonna pay? I too shoot on my own property (20 acres, not in my backyard) and would hate to think I was limited to just one gun. I don't have a huge stash of guns but I do so love shooting my 15-22, CZ 455 & 2 Buck Marks suppressed on my own land.
Of course it your decision, but you asked. I think it a bad decision to limit a suppressor, which is expensive & not easy to get, to just one gun. As stated, if you want to shoot high velocity, just get another stamp for the SBR. It will be cheaper in the long run & you will have lots of flexibility.
I don't doubt SBR is in my future.