That is very interesting...this is the exact set-up that I had planned with my installer...we had the Alpine PXA-H701 ordered...and waited for it over 3 months, until we got fed up and decided to redesign the system based upon the CDA-7998.
I was going to put the PXA-H701 in the exact spot you...
The dash piece in my car was custom made...this was done prior to the METRA dash kit that is now available.
It took my installer almost two days to fabricate this custom dash piece - he needed to make a mold of the front of the factory stereo to get the curves just right.
Total system cost -...
I thought you guys might like to see some other options for a custom stereo upgrade:
http://members.cardomain.com/booker3
Here is what my stereo system:
Head Unit - Alpine CDA-7998
XM Tuner - TUA-T020XM
3 Amplifers - all JL Audio - and all mounted in a custom amp rack in trunk on floorboard...