@alex1002 eBay.ca
The units are cheap and plentiful. You can either buy a bare chassis and all the pieces you want, or find a package deal. I found a good package deal that had all the pieces I needed. You can get 144 POE ports in the 5406 and 288 in the 5412.
Here's one with the premium layer3 license, and 2x24 port gigabit line cards and power supplies.
I'll warn you though, these things are good for layer2 and *basic* layer3. HP improved the layer3 capabilities with the v2 chassis and line cards, but the cost is quite a bit higher.
Oh and to answer your second question, 10GbE is simple with these chassis. Here's a
PDF with all the available line cards. The specific module you'd want for SFP+ is J9309A.
Hope that helps and sorry for all the edits!