Question about HCA-2 upgrades done by RAM


Hi. Looking at the archives, I have seen several posters recommending Reference Audio Mods for an HCA-2 upgrade, saying it made a huge difference in the overall performance of the amp. I like my HCA-2 (best amp in my system so far) and would love to hear it in an improved state. I found the HCA-2 page of upgrades on RAM's site: http://www.referenceaudiomods.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=PSAUDIOHCA2&Category_Code=MODS

Which of these upgrades result in the largest sonic benefit? I have heard of the $600 upgrade: what about the others (internal speaker output re-wiring, paper-in-oil capacitor option, digital power upgrade)? Which are the most significant for the money, and which are probably not worth the expense on a system that retails at about $10K? Thanks!
chiho
I have emailed the west coast modder and the general RAM website with questions and cannot get an answer from either one. Is this indicative of their customer service?
Just email Doug at RAM and ask. I think his reference amplifier is a modified HCA-2 .