I would say buy the original series now if you've been wanting it. I bet the price on them will skyrocket once the new series is released. The cheapest I found was on Ebay for The Final Battle & The Complete Series. The seller for The Complete Series was redtagmarket. The seller for The Final Battle was Moviemarz & redtagmarket. I think they're the same company, but moviemarz was the only one to combine shipping and The Complete Series was cheaper via redtagmarket. The original Mini-Series seemed pretty cheap too, but I didn't really look as I have that one already. There are 3 releases:
The Original Miniseries
The Final Battle
The Complete Series (this is only the tv show, it does not include the above 2 miniseries)
Can you tell I'm excited?