Hard Water filter advice. What is a good pre-Filter to add to my RODI system.

I just bought a RODI system on eBay.... (Hope I picked a good one.)

Anyway, I have hard water here in SA Texas. We get our water from the Aquifer. The water has lots of calcium in it.

What is a good pre filter to knock out the calcium before it gets to my delicate, highly sophisticated RODI system? I dont want to plug my RODI up with stupid calcium.,

Here is the specs on my RODI I just got.
REEF + HOUSE RO DI REVERSE OSMOSIS WATER FILTER SYSTEM - eBay (item 120375052504 end time Feb-08-09 09:04:04 PST)

I know I need a water softer for the whole house, BUT whats a cheap way to knock out the calcium for now?

 

Could I just get one of those magnetic eco-friendly filters that go around your pipe to turn the calcium into magnetically aligned calcium, Or will these magnetic filters not help because the calcium is still there and my RODI system has to filter it?

Here is the magnetic filter Im looking at.
WHOLE HOUSE SOFTENER WATER MAGNETIC HOME NEW GEN2 KITS! - eBay (item 300291874139 end time Feb-10-09 21:52:54 PST)