run a render and see what pegs at 100%
if you hard disk activity is the max that your hard drive benchmarks to then your hard drives are the bottleneck….
but if you have 4+ GB of ram then most likely your edits are all loaded into ram anyways.
I would bet that your CPU is the bottleneck for performance…
SSDs are great and will improve transfer speeds and programs so it is well worth it.
My advice is to get the largest SSD you can afford.
I use 2x240gb Intel SSDs in RAID 0
Sony Vegas Movie Studio
Intel i7 3770, 32gb, 2xRAID0 Intel 240gb SSD, 2x2TB WD Green, 3×23″ Samsung LCDs
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