Nice to meet you and I am glad to hear you're interested in the XenForo software. We can help you here on this community to get you a license. You can buy one on http://xenforo.com/purchase. They are currently $140 a pop Can't really get it any cheaper
IPB and vBulletin have always been the kings in the bbs market, but with XenForo they have a serious competitor on their hand. It's great to see more sites upgrade to a more modern solution, such as yourself, away from IPB to XenForo.
At http://xenfans.com we offer a convert service - and we do support IPB. Feel free to msg me for a quote. Once we get 50% pay up front, and the SQL to your IPB (and if you have attachments, the /upload/ folder as well. Then we can use our xenfans.inhouse (and/or impex) to convert you over to XenForo 1.0.0 RC2
It's about $35 for up to 250k posts, and if the import fails, you get the money back, minus an $8 base price.