A thermostat is rated on how many watts of output it can handle. Some are 500 watt, some are 1000 wat and some are 1500 watt. It doesnt matter how many things you have plugged into it as long as the load is less than the peak power handling of the unit. Plugging in a power strip will be fine, you just have to figure out what the power rating is on your thermostat and the power consumption on the heating elements.

I dont suggest using two different types of heating elements, getting them both where they are putting out the same amount of heat will be impossible.

I will suggest Flex Watt heat tape though it is very inexpensive..
http://www.reptilebasics.com/Heating-p-1-c-248.html

There are many guides on the net for wiring flexwatt, its easy... Then just tape it down will aluminum foil tape