Hi,
I Don't know what temperatures the one you have can reach - it really is a case of plugging them in and testing (nowhere near the animals tank for choice).
Well to make sure its ok you need to use either a thermostat or a rheostat.
Good recomended thermostats are;
On/off type (slightly cheaper slightly less stable but still good)
Ranco or johnson controls
Proportional type ( a little more expensive but a little better at holding temps and can control lamps too)
Helix or herpstat
You will probably be better off buying them online rahter than trying to find a local store that carries them unless you are quite lucky.
Have a searh on the forums for places people have bought them as I can only remember reptile basics just now and I know therte are alternatives as well.
It's personal choice but I owuld avoid buying the zoomed 500 thermostat (which it sounds as though your local shop might carry) as there have been reports of them being less stable with a temperature swing or up to 9 degrees and occasionally failing all together - its probably worth the extra money to get a better quality thyermostat as it is one of the most important pieces of equipment needed.
In the short term the lamp diummer from lowes has been used by some people with stable room temps just to make sure the mat doesn't get too hot as well and ( I think ) was only around $12 as well.
Bear in mind if you use a mat each side and a lamp then you will need some way to regulate each one but that a nice proportional might be able to do all of them if you connected dimmer switches inline between it and the lamp and cool end heat mat .
Have a look around for other peoples setups to give you an idea of different ways of doing it.
You might also want to consider a tub if you find getting the humidity and heat right in your tank too time consuming and tricky.
**edit**
Doh!! I'm typing waaay to slow this evening.
Pat it depends on the brand and model - I have some over here that are only capable of boosting temps by ten degrees but when I bought flexwatt I was stunned but how much it can pump out.
**end edit**
dr del