Equation Audio RP-22x > Sennheiser HD212Pro?

Hey guys, I've been looking for a new set of cans since letting my son have my Sennheiser HD212Pro's so I come check out the forum to see what gets alot of love here for $100 and less and the Equation Audio RP-21's got alot of love. So i'm looking in to those, reading as many reviews as possible and then I stumble upon the RP-22x's, which apparently are pretty much the same as the former with just a boosted low end from 5Hz-200Hz.....that seems right up my alley! I'm into loud and clean car audio systems, my current setup is

Alpine CDA-117 head unit
PPI 356CS front components
CDT Audio SQA-4100 mids/highs amp
Sundown Audio SA-12 12" subs
4cu. ft. ported box tuned to 30Hz
Sundown Audio SAZ-1500D sub amp

The problem I've been having is trying to get an accurate feel for how the music I put on my iPod will sound in my car. My PC setup consists of

AudioTrak Prodigy HD2 sound card
Insignia NS-B2111
JVC UX-G70 receiver
Sennheiser HD212Pro headphones

The bookshelf speakers sound good but aren't near field monitors so I don't get the good bass response up close....but if I take a few steps back it's a different story, the bass is lovely, but it doesn't dig as low as my car setup does. When I wear the cans, not much changes. So what's been happening is songs that I keep cause the beat sounds good on my bookshelf speakers/cans, fall flat in my car since both setups peak at a different frequency. And other times, songs that don't sound like they've got any bang to them slam like crazy in my car. So my goal is not only to have a pair of cans that sound clean and accurate but also can bang out the low notes with some authority so I can get a better feel for how it's gonna sound in my car. That being said, I decided to go with the more bass heavy of the two, the RP-22x's.

I have seen many complain of unimpressive mids/highs out the box and am aware of the quasi-Kramer mod some have done to help with that so that's an option if need be. I've also heard of some have new custom cord made for cans w/removable cords....what's the point of that? Will that help with SQ at all or is it juts to get a straight cord instead of the coiled one? Any suggestions on a moderately priced, superior performing cable vs. stock for these cans? Not sure what said cables go for but if possible I'd like to keep it below $20. Thanks for the help guys.