I don't currently have any interest in overhead environment diving, but deep diving seriously interests me.
Deeper, longer diving, involving decompresion obligations creates an 'overhead environment' as Cave Diver indicates, in that the surface is not immediately accessible (at least not safely). That point notwithstanding, I think I understand your focus. I pursued tech not because of any interest in caves but because I wanted to dive a little deeper (130-170') than recreational limits in order to see certain wrecks, and spend a little more time on those wrecks than NDLs allow.
I know this first question is the classic Ford VS Chevy battle, but I'm curious on everyone's thoughts on the best Tech training agencies.
As several have already suggested, the instructor can make a big difference, within any agency's courses. There are also differences among agencies in the sequence of teaching as well as some of the content, and you will get a variety of opinions. I happen to have done the DSAT sequence (Level 1, Deep, Trimix) which has many strengths and some shortcomings. Others have pursued IANTD, or TDI or another path. While we could recreate part / all of that discussion here, you might be equally well served by reading some of the (multiple) threads on the topic. Try a search using the words 'technical agency' and that will give you a good start, including several currently active threads on the topic.
In addition, now that you are Tech divers, in hindsight what would have done differently getting into it? What sort of planning do you suggest prior to your fist tech course?
Technical diving is very much about equipment, and procedures, and a mindset that supports appropriate use of the equipment, and adherence (rigorous and precise) to procedures. I will echo several of the points already made. Some things I would do the same, were I to start over. I started diving a drysuit early, which was a big help when I moved to tech, because I had at least some sense of DS bouyancy issues. I moved to a BP/W shortly after getting a drysuit, and adopted a long hose / necklace configuration, so that rig was well-known to me. I bought and regularly used a 40cf pony bottle on recreational dives (including some shallow reef dives in the Keys, which provided amusement for several boat crews) to get used to the effects of a slung bottle on my trim, and practiced gas switching, from backgas to pony to backgas. I later doubled up two HP120s, and dove them a number of times (quarry and ocean) before the first tech class. There are pros and cons to that particular approach (diving doubles before being formally trained to dive doubles) but at least I was not trying to learn doubles and a drysuit for the first time in the first tech class dive. As Jim suggests, that can be a bit of a bear. In hindsight, I would now do exacty what Lynne suggests, and pursue a DIR-F course. You live in a state where there are multiple DIR-F offerings, and I would encourage you to take advantage, not just to prepare for technical diving but to improve your diving skill in general. Like Jim, I would have spent less money on junk (including the very same 3 items that he mentions). I also would start with double 80s as Fixxer suggests, and not heavier HP steels. (I love my 120s, but my favorite coastal diving doubles rig is a set of older, cosmetically challenged, double 80s.) As you may sense from responses, there is not one (and only one) RIGHT way. But, there is some consistency in the experiences of others who have been down the road. Enjoy the journey.