I'll go from end to start...easier.

Yes, you should go to a 20L after the 10. Lower in height and easier to maintain. Also, a broken tank is just a disaster waiting to happen someday, especially when you add heat.

As for your current 10 gallon, that's a great tank for a baby but you have a few changes to make.
The pad is good, just make sure you get a thermostat for it ASAP if you don't have one already. Even the cheaper ZooMed ReptiTemp 500R ($30) is better than a dimmer.
A 100 watt bulb is WAY too high for a 10gal! Lower that down to at most 50watts if you're going to use a lamp and make sure the lamp itself is more than 8" above the lid.
You will want to get a digital thermometer, preferably an indoor/outdoor with probe, ASAP. Acurite are a great brand, found at WalMart and Lowes in the garden/outdoor sections for around $13. Those stick on ones are hugely unreliable.
You will want to include two identical hides, one on each end of the tank. These can be as simple as two plastic flower pot saucers with an opening cut out.

Here's a pic of my 10gal for my rescued pastel BP for reference:


Hope that helps!