This message was posted originally on the isp-bgp list, and I was told that it should have been posted on one of the network operator lists or a Cisco list if I really wanted advice on Cisco equipment from veteran network operators who have used this equipment extensively in the past for this application. Please, forgive me if this is not appropriate, but I hope that you will consider it appropriate and not flame me for my ignorance
If you're multihomed to the same provider, I wouldn't even bother with
getting an ASN and running BGP at all.
I assume they are providing your IP space as well...if so, let them
announce the route, and let their internal routing policy decide which
circuit delivers the bits to you.
Then, just configure two static default routes, to the two serial ports of
your upstream. In this scenario, you're current router should be fine.
Buy your router used, you're wasting your money otherwise.
To answer your question directly, there is essentially no benefit to
taking full routes from your provider from each location.