Servers which meet the following specs:

I am looking for a server with some very specific specifications, and I'm hoping I can get some suggestions here.

4 Hotplug Sata HDD slots.

Raid 5 capable on 3 HDD with 1 as spare.

1 U Rackmount.

Lights Out Management.

Linux certified (I know, Linux will run on just about anything).

Gigabit NIC.

1.8GHz+ Processor.

4 GB+ RAM.

HP Hardware preferred but not a deal-breaker.

I know the RAM and Processor specs are pretty basic but I thought I'd add them in the interests of completeness.

So, does anybody have any suggestions/recommendations?