Best Line Converter for Lexus?

I am kind of new to this. I had 3 systems done in my 3 previous cars, but never was too involved in the process of the who installation. This time I bought 01 GS430 Lexus and wanted to upgrade the sound. I wanted to leave the stock head unit, because it is connected to CD player and steering control, plus I like to have the stock look. I know in order for my after market amps (JL Audio 500/1 and 300/4) to work I would need to have a converter, I believe it is the line converter or someone also mentioned the Hi-Lo Converter. I guess what I am looking for is the amswer as far is which one to buy for the best possible quility of the sound. I was advised to get AudioControl LC6 or Soundgate. I also read the JL Audio Clean Sweep is coming out, but it is like $400. Any one has any idea of what to go with? I found this installer in NYC that installs top end equipment for top end german and italian cars. The guy was very knowledgable and said all the german cars he did were the owner kep stock head unit (Latest Benzs and Range Rovers) he used Soungate 4-channel line output converter LOC4.4. And he said sounded very good. This shop sells Focal and Dynaudio components and Genesis and Mcintoch amps, so I was more comfident with his work then other shops outhere. Also where would you install this converter to prevent the noise, I hear some of them install them in the back of your car where there is less wires from one of the speakerwires? Does that sound normal? I thought the converter will be behind the head unit.01 Lexus GS430 SOLD.. 04 BMW 545i Sport, NAV Logic7

I would use the Audio Control 6XS for this task. It will take either a speaker or rca type input from any type of factory audio system. Next it adds a dedicated sub output (with level control), adds separate output gain controls on all channels, adds a awesome 24db slope crossover, adds a internal grounding isolation circuit and best of all it does this in one small easy to use nice looking peice of equipment.Top Secret, I can tell you but then my wife will kill me.

Thanks guys.. I love this website. I got a lot of help from peple that know this stuff. Thanks..01 Lexus GS430 SOLD.. 04 BMW 545i Sport, NAV Logic7

THANKS MAN. I just called AudioControl spoke to this nice gentleman and he gave me a place that does LC6 and 6xs on all top end cars to go to get my system installed. Thanks again01 Lexus GS430 SOLD.. 04 BMW 545i Sport, NAV Logic7