Assuming you don't have hard bags on your 650, they're probably just the normal throw-over type. You would need new brackets specific to your 1300, but you could get those for well under $100 and then be able to mount almost any soft saddlebag. Unfortunately your seat will be incompatible.
I love my 650 and plan on keeping it until something that can't reasonably be repaired happens, but I also "upgraded" to a larger bike. Been spending much more time on the 1600 recently because I prefer the lower rpms and greater torque. Surprisingly, I have actually seen better gas mileage from the bike with 2.5x the displacement.
The transition took a little time because the bigger bike was so much heavier and more powerful, but the difference is amazing. Considering how soft the market is on used Yamahas, you can get an amazing deal on Roadstars.
The 1300 is water-cooled and a slightly different beast, plus some people say they still feel a little hurried at highway speeds. Only a test ride can answer that for you. Personally, I feel like a V-Twin should be air-cooled, and I'm super pleased with the 48-52mpg I get from my R*.
One thing is for certain...once you move to ANY of the bigger bikes. Your 650 will never feel quite the same again.
Ben C - Cary, NC
2001 XV1600A Road Star
2003 XVS650A V Star Classic