Apart from Avaya, the next best is NORTEL. They have a high up-time and have been in the market long enough to provide support.
NICE is a great tool. I have NICE and have been working with it for quite some time. If your looking at $$ — eventually, you will find that you get what you pay for.
If you are not going the Avaya route, Nortel is okay…watch it for the symposium system. Make sure they can deliver redundantcy. They told me to buy 2 systems if I wanted redundantcy. I sent RFP’s out to all the big players…2 responded. Avaya and Nortel. Don’t let Avaya kid you!!! Their costs came in under Nortel’s!!! that’s with Agt Access, NICE, Explorer, CentreVu CMS, Audix and the G3R…not to mention the T-server.