I had both and would say it's a deal worth taking. You can sell your SR on eBay for about $400 used, but if you have to buy the Note off contract it's close to $700 I think. As to whether it's $125 better than your SR - I think so. The screen size is great, and I think the phone just works a little better all around. I found the bluetooth on the SR frustrating - works perfectly on the Note. The extra functionality you get from the phone in general (sPen included).
I would suggest you would be happy if you do it.