This looks like a similar version to mine,
http://cgi.ebay.co.uk/SKYTRONIC-Regu...QQcmdZViewItem
Not sure about the control method on the first one, sounds complicated, the second, way to many knobs to figure out.. lol... in my opinon. Would go for at least 10 amps, you'll be glad you did I believe.
Radmaximus