You got those for a good price Steve. They were ten times what you paid new. However, have you checked the spec?
Here:
http://m.markertek.com/Attachments/S...ifications.pdf
They are not designed to produce deep bass. The drivers are fine, it's the comparatively small cabinet that will limit things. In a big box, they'd really deliver. It would be worth rehousing these.
If you are on a budget, you'd find a Denon PMA-350SE will drive them perfectly and to high levels, the PMA-350SE can be obtained for less than £100. You will need to use 'Speakon' connectors or fit some banana sockets to the boxes.