I've owned a couple of M1As, Garands, AR15s, and bolt rifles, though not the GSR.
I think a big factor is whether you want to use optics down the road. If so, the bolt action and AR are better suited for that.
While I like the M1 family, I prefer the two gun approach for all around utility and convenience and cost. Anything for the M1A is going to cost a lot more than the AR or bolt. Mounts, parts, barrels, mags, ammo. And it will be heavier. Lots heavier.
The AR has excellent iron sights, is cheap to shoot and can have excellent accuracy. It is better suited for most home defense purposes. A bolt action, not just the GSR, is much lighter to carry in the hills, can shoot a wider range of velocities/ammo, and is cheaper and easier to scope and will be more compact as well. You won't need abunch of high capacity mags for the bolt since you would have the AR. You can get an accurate Savage bolt rifle with scope for a fraction of an equivalent M1A setup.
As a lover of the M1/M1A it pains me to say it. I think a bolt rifle and AR is a more handy, versatile, and cost effective combination. But if I only had an M1 rifle I could still be happy!