I dont think its that great a deal. You could build an SL for only about $175.00-$200.00 more depending on where you buy the parts and how much they charge you to build the wheels.
Here's an SL Buy It Now for $845.00.
http://cgi.ebay.com/Cycleops-2007-SL...QQcmdZViewItem
Here's the exact same thing you're talking about for an $899 Buy It Now
http://cgi.ebay.com/CYCLEOPS-POWER-T...QQcmdZViewItem
Figure $65.00 per rim, $.75ea for spokes, and $45.00 for a front hub and you're into it for $1065 in parts..
Since Saris is in the process of updating the heart rate stuff and the Pro is being revamped anyway, Id buy new.