Yamaha DTXpress/DTXplorer/DTXtreme

Hi folks, I'm a guitar player trying to learn some drums for home
recording and getting more out of my drum software.  I also want as
good of a kit as I can afford laying around because as my guitar
playing (and gear acquisition) progresses I find it more and more
likely I'll be able to rope in someone to play with over here
regularly.  I pretty much have a complete basement recording studio now.

I got one of these Yoki DD-502 (osp, simmons, lloyd, etc) about a year
ago and have had fun messing with it occasionally.  It has heads that
can be changed to mesh, standard 1-zone 1/4" mono jacks, and I was
under the impression when I got it that I could upgrade the brain to
"real" gear and upgrade other things over time.

So of course now I'm eyeballing a DTExpress ii, iii, or iv brain.  I
want to trigger the brain with my computer software so that I will be
hearing the same sounds coming out of the same amp/speakers when I
practice drums as when jamming guitar along to my drum software
(Jamstix mostly).  

Has anyone gone this route of trying to upgrade one of these chinese
kits piecemeal?  Namely brain upgrade first?

I already found out about needing a new high hat pedal.  The DD502's
high hat pedal is just an on/off switch.  Even as a beginner I found
it problematic and really don't want to learn on such an arrangement.
 So that's great news really, although it adds to the budget.  I'd
also get a TP65S for the snare (or better?) asap and better cymbals
down the road if I get better at drumming.

Any other surprises lurking for me?  It's only a few hundred bux to
just dump the kit I have now and try to get a used Yamaha kit.  I have
a long history of doing things the long/hard/expensive way  8-)

Actually, what are some better snares I should look at?  I'm seeing
these things mounted on a real stand, seems like a great idea since
mine is fairly bouncy...  If I can upgrade this stuff one piece at a
time I'll probably go for the better stuff (like maybe the rhh130 for
the high-hat right off the bat?).

Ok, I guess that's a second question I have that I'm sure no one has
ever asked before  8-)  As a beginner to drumming, am I going to learn
bad habits on a crappy electronic drum kit versus learning on a real
acoustic kit or a higher quality edrum kit??  I do kind of hope to get
my drumming skills off the ground over the years.  For instance, it is
utterly laughable to expect someone to learn to play drums if the high
hat pedal (or the kick???) are just on/off switches, right?