i've had a lot of different head units over the years, and my best advice is this: pick the one you like the best!! as long as it's not a sh****y brand, you won't have a lot of trouble. you can get all the bells and whistles you want, but few systems are of high enough caliber to necessitate a ton of signal processing. things like adjustable delay times are sweet no doubt, but in the hands of people without rta's or trained ears, i think there's a pretty good chance they will garbage up the sound quality. stick with the big names, i.e. alpine, eclipse, clarion, panasonic, nakamichi, etc... then just pick out what you like or what you can get the best deal on. read some car audio mags. notice how most cars in there have different brands of head unit... makes you wonder.... my last head unit was an alpine. currently running a clarion dxz-716 and love it!!!