What would be a good decent 3 piece bow to purchase new for around $300 - $400.  I would like a 3 piece so I can switch limbs. Is a $150 Samick ok..?

The Samick Sage has a decent reputation. The Samick Red Stag is on sale at Lancaster and its supposed to be more refined than the Sage. There are a ton of high quality used takedowns out there in your price range like a Bob Lee Hunter for example. Good luck.

"There are a ton of high quality used takedowns"  not in my area and I dont buy online unless its local off a classified site.

Bought my son a Sage - #30 limbs for his 14th birthday.
I did a bit of archery and made my first bow back around 1969-70.
We both now have #60 Sages with a lot of arrows shot from them.
As for not buying on-line, I'm sure you have your own reasons for going that way, but if your concern is credit card skulduggery, an easy fix is to buy a Visa/Mastercard/Amex whatever gift card to use. That way you can never be ripped off for more than the gift card.
I've bought a fair amount of stuff from 3Rivers - arrow making supplies, B50 and what not. Good service so far.