Spoke to Peter @ The Server Store in Texas this week about the HP Proliant DL1000 G6. Appears to be a competing model to the Dell C6100. Unlike the Dell C6100, these appear to be the same layout as the Supermicro servers with the PSUs in the middle.
$1200 - HP Proliant DL1000 4X DL170H G6 Servers 8x L5200 CPU's 128GB Mem 8x HDD Trays | eBay
$2100 - HP Proliant DL1000 4X DL170H G6 Servers 8x X5560 CPU's 128GB Mem 8x HDD Trays | eBay
For the price, the DL100 is a bit more expensive AND I don't think you can hot swap all of the nodes which is a bummer.
$1200 - HP Proliant DL1000 4X DL170H G6 Servers 8x L5200 CPU's 128GB Mem 8x HDD Trays | eBay
$2100 - HP Proliant DL1000 4X DL170H G6 Servers 8x X5560 CPU's 128GB Mem 8x HDD Trays | eBay
For the price, the DL100 is a bit more expensive AND I don't think you can hot swap all of the nodes which is a bummer.