Wow, I didn't expect to see so many comments here, thank you to all who responded. Just for clarity, we're not looking for VoIP end-to-end, we still plan to go out over a PRI.
A windows-based system like the Vertical TeleVantage just seems like a bad idea to me. Despite being a Windows shop, I like the idea of a phone system not having all that Windows overhead.
I suppose in the end, we'll go with a hybrid solution as it allows everything we need without complication. Although, if the 3com v3000 is competitively priced even with switch upgrading (as we're due for an upgrade anyhow), it'll be a tough choice.
Thank you for all of your comments!
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space travel's in my blood.