Do you buy gear new, used, both?

Both. A fun part of this hobby for me is adding and upgrading equipment over time.  I’ve bought new, used, demos and open-box equipment.  Always looking for the next deal.  Buy for myself or for family and friends.  Also enjoy selling used gear or giving it to family and friends. 

I forgot my small 5.1 Home Theater.

New: TV; AVR; BluRay; Front L/R Speakers (DBX 100's mentioned above)

Used: Center, Sub, Surround L/R

My system is mixed.  Mostly used, but some components were new.  

Mostly used. I've purchased from TMR, USAM, High Performance, and Echo. I do a lot of research and communication with the seller, and always negotiate a better price. I typically pay around 55% of retail and only purchase current or recent models. I would estimate I've purchased $35k retail value for $22k. 

I've had great luck I suppose because everything I've purchased has looked and performed like new. I've had no issues with any of them. YMMV

doesn't matter really, it's with the tech