I don't have enough experience with the more economical XRite products to be of any help to you. In general, I would say the minimum you would need for any CMS work would be the i1 Pro. That is, of course, if your display had a color management system. If it does not, a meter that does color measuring won't be of much benefit to you in the short term. CalMan does offer the ability to measure primaries and secondaries and you can set your color and tint using the software. To me personally, I find it to be a bit time consuming, and I don't use this feature. I use color filters like the majority of people and then view reference material and set the color control in the user menu by eye. Your call though as to whichever works best for you. They all do an adequate job on average of setting the grayscale until you get into the lower IRE's, but the vast majority of economical meters have trouble below 30 IRE anyway. CalMan does offer a low light algorithm to aid meters in doing this. Like I said, the precision and accuracy of the meter are what remain the question. You may get a good one, you may not. Without testing it against a known source, it is hard to say which one you got. I will say, that whatever direction you choose, the results will likely be more accurate than they are right now. Just how accurate do you want to be is the question. Squeezing out that last 10%, which in video displays can be significant, is where all the arguement and discussion often lies on this forum.
Regarding CalMan vs. HCFR, which one would you say is the best to go with? Paid program with customer service and software updates readily available, or a freebie where updates are whenever they get around to it? If the good folks over at Spectracal are offering you a good package deal on software and hardware (display LT/2), I wouldn't think too long to grab it...especially since the price will be going up in May.
As far as the uber ISF/THX calibration is concerned, to each there own I guess. What you get with a professional is often a vast amount of experience making the errors over time and learning from them, often more accurate instruments and other equipment to make your display as accurate as it can be and experience using them, a solid understanding of display technology and the science behind it which took years of learning, and on and on. I don't know, is that worth $300-$400 to you? Since you'll be spending $300-$400 on equipment anyway, spending quite a while learning how to use it proficiently, experimenting in the service menu and quite possibly irreparably damaging it, and spending quite a few more minutes and hours online in this forum trying to piece it all together....as Michael always says...how much is your time worth to you? I guarantee you'll be running somewhere to get the answers and spend quite a few hours, days, weeks, years doing it. Is that worth $300-$400 to you just sitting back with a beer in hand and letting a professional give you peace of mind it will be done right? You can also quiz them as they are performing the calibration and pick their brain to see if it really is something you want to charge headlong into.