"TRIM probably* does not work"
you are correct on this. You want SSD with good garbage collection, I think majority have it (certainly Crucial and Intel do).
Anyway if you marry SSD with RAID, your contention is going to be RAID bandwidth anyway (unless you set the limit to few drives only). Modern SSDs are really much faster than HDDs and RAID cards can "feel" it. Also only few RAID cards support SSD, e.g. newer LSI.