Hey David,
I think what this boils down to is partially also your comfort - I can completely see how you like the online price better...
As far as teh regulator - figure that it is about $80 a year (parts and labor) for service - and as you know - life support equipment is probably on the list of stuff you want serviced - f you buy from the LDS and get the warranty, the labor is covered (either that or the parts - about half the money) - You might have hear the spiel about the cost of ownership over 10 years... And I bet you that if you buy the stuff online and then bring it in to get it put together, you will pay a premium price for that job.
Another thing to consider is the fair market to the LDS, how did you arrive at all this equipment being what you wanted? Lemme guess - the guy at the LDS helped you figure that out - he invested - likely hours in your choice of equipment - now imagine that you come marching in there with what he suggested you get and need help after you went out and got it somewhere else...
If I was you - and especially since you are looking at equipment that you don't want to break - I would probably go to the shop and get it. Remember if something is wrong with that computer - you will have to ship it back to DiveInn... becasue the shop guy is going to laugh his way back to the coffee pot after he tells you how much money he wants to even let you bring it into the shop...
I think that your setup looks very nice - I also noticed that you don't live right on the ocean (ok, my knowledge of american geography is limited so I may be wrong - but it is my impression that Ohio is landlocked...). I bring this up because you are looking at top of the line regulators - sure - you should buy the best you can afford, but I have to tell ya, unless you are going to be working with this stuff, you don't need the best money can buy and even then - the TX50 is what is recommended for technical or the ScubaPro G250 - I would say you can save some money with a TX50 and make the LDS guy happy AND get great service, get the TX20 for your secondary and you will be all set - you could even consider the R380 from Scuba Pro - I think it will serve you just fine for a long time... Anyway - this is just my opinion.
I personally dive G250/mk20 and love it - and it was cheaper than that new stuff and have a much more positive purge button (the main reason I personally don't care for the 550 or 600).
One last thing - there is a thread here about DiveInn and some people who had issues with them...
DiveInn thread
That's it (for now)
Big T