I've got a scope and a V5 I-Opener... I don't have a hard drive for the V5, and since legacy audio support is absent from the BIOS, there is no chance I can get the thing to make any kind of noise in DOS. Anyway, I don't need any audio mod kits or anything in return... Just tell me what points you want tested and I'll tell you if there's a waveform and what the voltage is.
On my mutant v2 (a v2 with a Hitachi screen, since the I-Opener fell over and I had to replace the screen), I just followed the LM---- (having a brainfart here, can't remember the rest of the numbers and don't have an opened I-Opener handy to look at) application circuit for a headphone jack. I don't know why people have said the output is low quality - I've connected it to my RadioShack Pro 35 headphones (the Titanium headphones, they're actually made by Koss and sold at Circuit City for $19), an el-cheapo cassette adapter, as well as my home stereo amp's line-ins and experienced great sound every time.
Ironically, just as everyone has finished their car I-Opener MP3 players, the market is getting hit with portable MP3 CD-R/RW players, some for as cheap as $99. When you factor the cost:
MP3 CD-R/RW player - $99
CD-RW Burner - $99 (Tigerdirect.com has some for less than $99)
13GB worth of blank CD-Rs (20) - $16
I-Opener (Original Cost) - $99
12GB laptop drive - $160
I-Mod Kit - $35
Tennmax Fan - $22
Power Inverter - $19
Not including time to do hack or cost of parts for audio out hack or a USB NIC for MP3 transferring, the total is: $335