I don't find the options that helpful - not least because I presume by Opix you mean Monaco OPTIX XR.
I use OPTIX XR Pro - that, and Gretag Macbeth Eye-One Display 2 seem to be the two highest rated products overall (excluding specialist products that only calibrate certain monitors). They're also owned by the same company now - X-Rite, the company that owns Monaco, has bought out Gretag Macbeth.
The higher end Spyder products seem to come very close in comparitive reviews - but maybe fall a little short.
The cheaper solutions such as Huey work, and may be adequate for amateur use.
Probably a more important question is what sort of monitor your have. If it's a 6 bit TN based LCD, I'd spend money on a new monitor before trying to calibrated what you have. TN monitors (which includes every laptop panel I've ever used) tend to be rather poor for colour critical work, as the colours change as you move your head around the monitor.
I use a Dell 2005FPW, which is an 8 bit S-IPS based LCD. IPS is the best technology for colour rendition, closely followed by *VA (MVA and PVA). There's a database here that allows you to look up your monitor.