Cisco IOS Router Vs. ASA Firewall For Small Colo-racked Setup

I am in the process of gathering the peices to move from a dedicated box to my own hardware in a local colo and am undecided how best to choose the edge device.

The colo has a 30Mb pipe with about 10Mb of it being constantly used during biz hours. Another 10Mb is being allocated in the next couple of months. I want to be able to burst to the full 30Mb when needed.

I am getting 12 IP's allocated but will increase to 24 soon if all goes well (fingers crossed!).

I will have for starters just a single Proliant running dnp on 2008 with IIS, FTP, Mail, ns1 and a 2003 VM running my secondary ns.

What I am unsure of is the edge device and looking for others that have used either a 2800 series router or a ASA5500 series firewall in a similiar fashion. I know what the raw throughput of each device is, but raw benchmarks are not realworld numbers by any means.

I am looking at the 2801 with IOS Firewall turned on and hopefully even some inspects for FTP and HTTP traffic. The other option and one that I am less familiar with is to use the ASA5505 instead which will do my basic routing but supposedly provide more thourough inspects and advanced rules.

Does anyone have experiance with either of these in a hosting environment and have input on the realistic throughput one can expect from either device?

There is a signifigant cost difference with the ASA5505 being much cheaper but I am more familiar with IOS. Would anyone recommend a 1841 router instead?