XAVB2602 & XAVB2001 compatibility

[Kizzinger]

Hi,
Sorry for my bad English but I'm Italian and I'll try to explain my situation.

In January 2011 I bought a XAVB2001 kit, and it worked fine (120 mbps average speed).
Now, in order to connect also my notebook and my PS3 to the home network, I've just purchased a XAVB2602 kit (http://www.netgear.com/home/products...XAVB2602.aspx#) and this is my actual configuration:

XAV1601 --> modem router
XAV2602 --> pc desktop & printer
XAV2001 --> pc notebook
XAV2001 --> PS3

While the two new adapters XAV1601 and XAV2602 work great (150 mbps average speed) probably thanks to the filtered sockets, the two "old" adapters XAV2001 have become very slow (about 60 mbps).
I can't understand why...

Looking at the list of powerline products compatible with my new kit XAVB2602, I found "AV 200 ULTRA SET (XAVB2001)".
Well, my first kit is XAVB2001 too, but it's not ULTRA. Could it be possible that I've got an old version of XAVB2001, and only the new ULTRA version (http://www.netgear.com/home/products...xavb2001.aspx#) is compatible with XAVB2602?

Thanks for your answers.
Gabriel