It's a mixed bag but generally speaking a typical everyday user or gamer does not require or need mutiple ssd's in a RAID array. It would be different if you were doing some sort of special professional or scientific work.
You are right about losing the Windows 7 TRIM feature. In a RAID array the Windows 7 TRIM feature is not recognised by the ssd's. The ssd's must rely on their own garbage collection process. The ssd garbage collection has changed quite a bit. Modern ssd's have more aggressive garbage collection but the opinion seems to vary about how much the process has improved.
There were reports that a way has been found to allow ssd's in a RAID array to recognise the Windows 7 TRIM feature. However, I do not know how much progress has been made.
Since you already ordered 2 ssd's you could do something really cool. You have the means to conduct an experiment and find out what works best for you. Go ahead an try both configurations and see what happens.
just thought I would mention that write-caching is disabled by default for ALL Intel raid array's since many don't realize.
2 ways to enable it. 1 is with the RST raid app.. OR.. go to device mgr/drive properties and uncheck the write-caching>click OK>recheck>click OK. Retest and watch the write caching to RAM pump up the scores.