The pond pumps are not going to create any more pressure, and your system is not going to work any better. You are thinking (as I once did) that Greater GPH=Greater Pressure. It doesn't. Flow does NOT equal Pressure.
The pumps that you are looking at are NOT designed to create pressure--especially in what amounts to a closed system. pressure will simply reduce flow rate--which is what u already experienced before.
They make pumps that are designed to create pressure, but I'm thinking their cost is out of this ball park.
My suggestions are these:
1) buy a commercial 5-gallon bucket system and forget about it,
Or
2) (what I did) T into a water line in your home--bathroom sink, kitchen sink, whatever. Use adapters to get from the T size to Icemaker tubing size--run your tubing wherever you need to, use adapters to get back to garden hose size, use one of the programmable waterhose timers (walmart, etc) for your automatic valve, use adapters back down to the size that you need for you misthead and then run it to and place your misthead. You won't find a better system for the money. And You are not going to generate better pressure from a pump. Plus expansion is wide-open---you can run a whole BUNCH of mistheads of that one setup.
The hardest part is coordinating/finding the adapters to go up and down to different sizes, because you will end up using both PVC and Brass. You should be able to find them all at one good hardware store though. Don't forget the teflon tape.
Example of the Garden hose Timer: http://www.homedepot.com/prel80/HDUS/EN_US/diy_main/pg_diy.jsp?CNTTYPE=PROD_META&CNTKEY=Products_2/Garden Center/Watering/Timers&BV_SessionID=@@@@0160990629.1085887371@@@@&BV_EngineID=ccdfadclilfddhecgelceffdfgidgjj.0&MID=9876
If You want to use sprinkler cylinoids--then you can find a timer these days that will offer a min mist time as low as 6 seconds. In some cases, 1 minutes minimum is simply TOOOOO much water.
HTH