Which AGP-Radeon-HD card delivers surround-sound via HDMI

Hello : some support and advice needed ...

sorry, it is a little wordy, but I wanted to provide plenty of details.

Thanks ...

for background : I am attempting to improve/upgrade
a HTPC connected to HDTV(1080p) &
a 7.1 Surround sys. (w/all the Dolby, Digital, THX, stuff, etc..) ...

PC specs:
Dell Dimension 4600, 3.0Ghz, 2.5GBRAM,
WinXp-Sp3, 500MB HDD, (550w PSU)
Sapphire Radeon HD 3650 (AGP)
ASUS Xonar-DG pci-audio card
( DVD player is coming )

current configuration:

PC-audio(ASUS Xonar-DG) is connected via Digital-Optical Cable to the 7.1 Surround A/V Receiver. I get clean audio-sound, but only stereo at best. ASUS techs confirm that this audio card can provide ONLY '2-channel' audio over the optical cable; contrary to the card specifications!
and ...
PC-video to HDTV on 45ft of DVI-HDMI cable works up to 720p resolution. But HDTV reports 'out of range' when attempt 1080 resolution.

I would like to achieve full 1080 HD and true 7.1 surround-sound over HDMI using premium 22awg 50' HDMI-HDMI cable w/Gold connectors.

My searches have shown I have limited options for AGP-video cards with native HDMI connector and built-on surround sound.

* quoted from HISDIGITAL website
http://www.hisdigital.com/un/news_show-73.rhtml?height=400&width=780

"...ATI Radeon HD 4800 & 4600 Series graphics card ... providing a seamless connection to an HDTV or home theater system. With built-in 7.1 surround sound audio (AC3 / DTS ) ... support single cable connection directly to a compatible HDTV, projector or receiver ..."

* (searches have failed to locate any Gigabyte user-manual or
specifications regarding audio over HDMI)

* The online consumer reviews (AMZN, NWEG) and support-forums
regarding HD-audio on HDMI with AGP cards are spotty and conflicting.

So, given all the above ....
Which of the AGP-Radeon-HD cards below
would be recommended
and will provide
discreet HD-audio surround-sound
via HDMI on my system?

==> GIGABYTE Radeon HD 4650 AGP 8X (GV-R465D2-1GI)
1GB 128-bit GDDR2 HDCP-Ready

==> HIS Radeon HD 4650 AGP 4X/8X (VH465F1GHA)
1GB 128-bit DDR3 HDCP-Ready

==> HIS Radeon HD 4670 AGP
1 GB DDR3 Native HDMI (H467QS1GHA)

========================================

regards
O.T.

The HD 3650 GPUS only support 5.1 channel surround sound. For those cards i would suggest the Gigabyte HD 4650 or His HD 4670. but the gigabyte is cheaper so get that one.

____________________________-
Sytem Specs :

MB: intel

CPU: intel pentium 4 2.8GHz

Memory: 2.1 GB DDR 400MHz

HD: 2x 80GB Maxtor IDE 5400rpms

GPU: ASUS HD 3650 512mb GDDR2 agp @ 8x