Using N900 Wireless router as WAP on Wired Network: Speed Issue?

I have been having a heck of a time getting my gigabit network working off of either my new router, or 2 older ones. Since my house is wired with cat5 cables, I was thinking about putting an 8port router in my networking box that is tucked away in the corner of the house, and then using my new Dlink 857 router as just an access point in a more optimal location in the house.

My questions are as follows:

Would be slower for either the wireless internet speed or the speed of file transfers between the wired computers?

Would I be able to transfer files both ways from the NAS that would be hard wired to the 8-port router?

Is there any benefit/disadvantage to my idea that I have not thought of?

I know it is possible, but do I want to do it?

Internet----->Cable Modem --------->Wired Router --------> Xbox/NAS/PS3/Smart Player/Dlink Router set as Access Point