A print is intrinsically a different medium than a computer monitor, so there will always be an irreducible gap between them. However, you can get pretty close allowing for the luminance of the monitor against the lower contrast range of the print.
A calibrated monitor is critical, and the Spyder 2 is more than good enough. However, PrintFix pro, like all other scanner-based printer calibration, simply cannot compensate for varying ambient lighting. Results will always be mediocre and inconsistent, leading to a lot of trial and error with attendant ink wastage. I know, because I've tried! You have several choices for getting a reasonably good printer profile. You can spend the $1,500 or so needed to get a spectrophotometer-based profiling system, or you can obtain profiles from someone using such a system. There are many vendors out there who will generate a profile for you, usually for about $50 apiece. Or, you can splurge on a printer that comes with good profiles out of the box, like Epson's 2400/4800 etc. Or, you can spend money for a RIP like ImagePrint that comes with excellent profiles for your 2100.