Line out Converter recommendations for budget installation

[ksagis]

Wondering if folks have recommendations on a reasonably priced line out converter for connecting to base head unit in my Roadster.

Details on my planned install for upcoming BigAudioFanat install trip to Socal:

-Base headunit (want to maintain stock HU for crime given Roadster)
-??? line out converter
-Precision Power P900.4
-Front speakers Polk MM6501
-Rear speakers Polk db351 (yes, sound stage, I know)

I was looking at the Audio Control LCi2 and Rockford Fosgate RF-HLC or RF-HLC4. Folks seem to like the LCi2 but don't see any reviews on the RF-HLC series.

I'm shooting to keep the total for hardware somewhere around $500 and not sure if the Audio Control for $100 is appropriate given the other components I'm looking at or is perhaps overkill.

Advice on LOC appreciated as well as overall thoughts.