Sounds like you've got a fantastic system in the works. One thing to note is how power hungry those polk rti12's are. The 435 is a pretty beefy receiver and I don't think you'll have too many problems but later down the road you may want to go with a seperate amp for the front two speakers. The 435 will allow this and it's a pretty upgradeable system.
Is the Velodyne at half cost as well? Do you know the model number? Velodyne makes some fantastic subs and some not so fantastic subs. They are usually a pretty good bang for the buck but like everyone else on this site I'd suggest you look into HSU, SVS, etc.. beforeyou go 100% with the Velodyne. Of course if this is a higher end Velodyne and you are getting it half off then there is no sense in complaining.
I really think you'll be happy with your choices. You will have some great sounding 2 channel audio and some fantastic HT sound. Good luck with it all, I think you'll even wind up impressing yourself with your coices.