A bunch of years ago when I moved into my apartment I picked up a cheapy HTIB solution from Sony (HT-DDW900).  After getting annoyed with the receivers poor HDMI compatability I upgraded to a Yamaha RX-V367 (Link) which gave me a huge improvement from the speakers the unit came with.

I was just over at a friends place who had three Energy speakers in his setup that blew me away (L/R, Center) and I knew it was time to upgrade my speakers.  I just picked up a pair of Energy CB-5 (Link) for my front L/R and I am looking at a pair of lightly used NHT Zero A-400 series to replace the rears (around $80 for the pair)

I know the NHT Absolute Zero's have gotten great reviews, however these seem to be a much older model from circa 1997, does anyone have any info about them?

Should I just leave my rears satellites as is, and replace my center channel first?

 I am kind of tight on space as I live in a studio apartment in Brooklyn and my entire theater area is 15'x15' so I dont have room for huge speakers.

I'd Love to hear your thoughts.

Thanks.