Unfortunately with the MVB you cannot use a rheostat, so I'm told. That has always been the one thing that has up until know stopped me from getting a MVB (fear of the temps getting to intense). I still have never had a MVB, but plan on getting one in March, and I've heard plenty good about them. Heres an idea that migh work for you it will cost you between $12 and $14. First is to buy a lamp dimmer (which is the same thing as a rheostat minus the word rheostat and the picture of the lizard on the box) the second step is to get a light literally called a "heat lamp" I got one at walmart for $4.14 it is a 250 watt.
I assume you have a clamp lamp, but you'll need a big one to accomodate the 250 heat lamp. these heat lamps are designed for warming bathrooms and keeping food warm, so naturally I was suspicious at first too, but it works fantastic and cuts down on the electric bill. I use it in my Mali Uromastyx's tank (they like their basking temps a little hotter then beardies. Okay heres the warning. Once you plugged evething in, NEVER turn the heat lamp all the way up on the lamp dimmer if the distance is less then 28 inches away from the beardie. When I was testing it in one of empty feeder tank at 16 inches at max it brought the temperature up to 175F. So be cautious when setting it up, and I suggest taking a marker out and marking on the dimmer where it should be to be safe yet effiecent (I even broke my down into different temps on the dimmer and it is very reliable for that, and change it for dawn dusk and midday) Once you got it setup and checked the temps its a reliable as 'Ol Faithful, and you don't have to worry about it again.
If you are set on getting a MVB then I would get a low wattage one and also have a regular heat lamp with a dimmer attached to it so you can regulate the temps, or like ypu said a CHE (heat emitter) with the dimmer, either are fine.
Hope I helped!
