I have a Stock 05 BF 750. I ride with a guy who has a polaris 800 EFI it rides much smoother in the little bumps then my BF. Would new tires help? I was thinking Big Horns?

 

Maybe if you found the right tire it might help a little but for the most part your not going to find tires much smoother than stock ones. The reason your brute is so rough is because it is a brute force. The polaris 800 has a much more plush suspension than the brute force. I own a brute and they are great on power and they still have a nice ride, but their not the smoothest by far. Well good luck!

 

The polaris has the most comfortable ride out of all of them while the brute is down at the bottom end of the comfort spectrum... aftermarket shocks will make it handle and ride like a completely new bike but they cost money.(think you can get the cheapest set from works for like 800-1000)

Only other option is to remove the rear sway bar... it is incredibily stiff and doesn't let each tire work independantly at all. The only downside to this is it might make the bike more tippy but some like it and others don't.

 

xGoatMan is correct.
The WORKS shocks will smooth out the ride, big difference in every department. No comparison at all with the stock shocks, the aftermarket Shocks make that much of a improvement.
Cost, not cheap fix. Basic WORKS Steeler ATs built for you directly from WORKs, right near $800 for all 4.
Add the adjusters and the remote Res'es, then the price is around $1225 for all 4.
I 1st just went with the Basic WORKS Steeler AT's, excellent results. Just recently I returned my WORKS to "WORKS" to have the adjusters and the remote Res'es added on, nice that WORKS allows these two options to be added on at a later time if you feel you need them or when the extra $$$'s come available.
WORKS also has the G-Series available.
Click on the Camera to the Left,my WORKS Shocks are there.

Haven't messed with the rear sway bar yet but am thinking of taking it off and comparing the ride, handling to my present set-up.

 

I'm thinking I might have to upgrade my shocks for a better handling/smoother ride on my bf750. I read that the bf650 has a softer seat than the bf750? Does anybody know if the bf650 seat will fit on the bf750?

 

The seat should be the same from the 650i to the 750i.
You can fix the BF750 seat yourself, the same way I did.
Remove the seat cover (Pull stables out), cut out some of the way too firm seat foam, replace the cut out section with a 3/4" thick piece of raw Gel-pad (JCWhitney carries it), restaple your seat cover back on and now you have a real comfy seat.