A couple of years ago Aastra launched a small form factor PBX based on Asterisk, the AastraLink Pro 160 Small Business IP PBX. This was a sub-$1000 solution for small businesses. The IP-PBX is XML based so that it can be customized for small businesses. As I have written before, I think the numerous ITSP's are missing out by not taking advantage of the XML in the IP Phone handsets.
snom has released its new IP-PBX for the same market - up to 20 extensions for about $550. (AastraLink is up to 50 extensions for about $800.)
snom also launched the affordable IP 710 phone, which offers wideband audio, better known as HD Voice.
snom will be at ITEXPO next week.
Interesting that Aastra offers phone specifically for Microsoft Lync. The phones do some signalling between the handset and Lync.