Suggest a 7" touchscreen to get started?

I apologize for yet another 'what LCD' thread. I've read up on the subject but am quickly getting lost in a lot of the techno jargon. I can look up what the technology is and how it differs from others, but trying to make a informed decision based on subjective observations is a bit difficult. Anyway, here's my situation; I'm just getting started in carputers and want to get a fully working system on my bench to make sure I can get it working the way I want to and will be satisfied with the results before I commit to installing the hardware in my car. I'd like to get a touchscreen to start testing with the expectation that I'll probably upgrade it should I commit to the project. Also I feel that if I have one in hand and have some experience with it I can make a better informed decision on what features I need and what I don't when I buy for the final install.

Am I wrong in assuming that they all pretty much work the same from a computer functionality standpoint? For example if I get a brand 'X' screen to play with then decide I'm going to go with brand 'Y' for the final install will all settings and functionality be preserved (drivers not withstanding). This will also give me a chance to see what one looks like in my car in real life to see how crazy I need to go with anti glare/sunlight readability. Maybe the random one I pick up now will end up being good enough? One thing I know I definitely want is to be able to control the brightness externally - tied in with the dash lights. I'm not an electronics pro by any means but I can handle certain things like if I need to make a voltage to PWM circuit to drive LED's etc.

Again sorry for such a broad sweeping question.

Thanks,
Ryan

for a base screen, i would look at the 701/629(the internal components are the same, the model numbers just reference the different bezel's). i've got 4 different screens(that one, 2-669's, and a usb screen), and my 629 is the most bullet-proof of them all.. the only reason i upgraded is because i have a convertible. with a standard-roofed car, i think it does fine.

also try to make sure to get the led version-- i think they might have discontinued it, but some models use ccfl backlight, which wouldn't be as easy to externally dim.

Thanks. I've been doing a lot of searching/reading and running myself in circles. I was planning to go with the cheapest thing I could find just for experimenting with but I think I'll take a stab at getting something with hopes that it'll be good enough to use for the final install. I've been researching the Lilliput 669GL-70NP/C/T-HB-RV. It seems a lot of people like it. Big thing right now though is I haven't found anything yet about how to control the brightness externally. Also the bezel for my car appears that it will be a perfect fit fir the screen itself but that would mean all the buttons would be inaccessible - though I notice a lot of other's installs are the same. Once the initial setup is made is there any reason to be able to access the buttons?

my biggest beef with the 669's is that it doesn't seem to like to play nice with my zotac geforce 9300 board across all input formats.. overall, i like the input format flexibility..

there isn't too much documentation on external brightness control, but it shouldn't be very hard-- the raw led's are connected to the board via a single connector, so all that it would take is like you said-- a basic transistor-based pwm circuit to interupt one of those wires, or you could go full-bore and build your own pwm power supply.

i don't know the voltage that the led's run at, but regardless, it shouldn't be that hard to create..

for the buttons, no you really don't need them-- even for the beginning setup-- all the screens have a IR remote, and all the settings i have ever needed to access-- including the hidden menus on the 629 are accessed via the remote, so as long as the IR reciever is visible, you can really ditch the button panel all-together.

I just got a pair of e350 boards so it's ATI for me. Up till now atleast I've had zero issues with ATI and setup so I'm crossing my fingers.

Yeah I haven't been able to find anything on external brightness control. If they are readily accessible through a dedicated connector like you say then it shouldn't be too hard at all. I'd still like to find a pin out/schematic of that though before I start futzing with it - or even before I commit to buying the unit in the first place so I know I'll be able to make it do what I need it to. I haven't used them in a while but I imagine a 555 circuit will work well for the LED control - I also have some older SMPS controller IC's that might be able to do this as well and possibly easier than a 555.

Do you need to use the remote in normal operation or just for setup purposes? Though I'm not sure what there would be left to control if I supersede the LED brightness circuit.