Just built the PC last year? I wouldn't upgrade that for another couple of years...but then again, I'm not you. I'd suggest a console as well, especially if you enjoy gaming with friends/groups and that's where they are.
PS used to have the argument of a free online aspect. I don't believe that's the case anymore. While there are no killer exclusives on any system besides Nintendo stuff), I've always preferred the Halo franchise. You mentioned Gears, but I've heard of no new games for that franchise for the future.
Buddy and myself have been hitting Destiny for awhile now. The multiplayer aspect was done very well.