Granted this thread started on 2/6/05, but I'm just not seeing the price differential you were quoting.....
I'll be building my first system in March and I conceptually built these systems (all prices are as of yesterday at NewEgg except the case and LCD which I have already purchased and are my actual price):
Socket 754 System
SOLTEK "SL-K8TPro-754" VIA K8T800 $106.00
AMD Athlon 64 3000+, 512KB L2 Cache 64-bit Processor $147.00
Kingston 184 Pin 512MB DDR PC-3200 - Retail $69.58
SAPPHIRE ATI RADEON 9600PRO Advantage Video Card, 128MB DDR, 128-Bit, DVI/TV-Out, 8X AGP, Model "100561 GR" -BULK -OEM $103.99
Seagate 80 GB Barracuda 7200RPM SATA with NCQ Hard Drive, Model ST380817AS, OEM $73.69
NEC 16X Double Layer DVD±RW Drive, Black w/ Software, Model ND-3520A, OEM $66.49
Microsoft Windows XP HOME Edition With Service Pack 2 -OEM Specifications: Designed exclusivel...... $93.94
ImageQuest L90D+ 19" LCD Monitor w/ Speakers, 8ms and DVI ?RETAIL $388.00
Antec Solution Series Quiet Black Mid Tower Case with 350W Power Supply, Model "SLK2650-BQE" - Retail $45.50
$1,094.19
Socket 939 System
SOLTEK "SL-K8TPro-939" VIA K8T800 $113.99
AMD Athlon 64 3000+, 512KB L2 Cache, Socket 939 64-bit Processor - Retail $158.00
Kingston 184 Pin 512MB DDR PC-3200 - Retail $69.58
SAPPHIRE ATI RADEON 9600PRO Advantage Video Card, 128MB DDR, 128-Bit, DVI/TV-Out, 8X AGP, Model "100561 GR" -BULK -OEM $103.99
Seagate 80 GB Barracuda 7200RPM SATA with NCQ Hard Drive, Model ST380817AS, OEM $73.69
NEC 16X Double Layer DVD±RW Drive, Black w/ Software, Model ND-3520A, OEM $66.49
Microsoft Windows XP HOME Edition With Service Pack 2 -OEM Specifications: Designed exclusivel...... $93.94
ImageQuest L90D+ 19" LCD Monitor w/ Speakers, 8ms and DVI ?RETAIL $388.00
Antec Solution Series Quiet Black Mid Tower Case with 350W Power Supply, Model "SLK2650-BQE" - Retail $45.50
$1,110.18
Socket 939 System PCI-E
SOLTEK "SL-K890Pro-939" VIA K8T890 $127.00
AMD Athlon 64 3000+, 512KB L2 Cache, Socket 939 64-bit Processor - Retail $155.00
Kingston 184 Pin 512MB DDR PC-3200 - Retail $69.58
Albatron nVIDIA GeForce 6600 Video Card, 128MB DDR, 128-Bit, DVI/TV-Out, PCI-Express, Model "PC6600/128" - Retail $119.99
Seagate 80 GB Barracuda 7200RPM SATA with NCQ Hard Drive, Model ST380817AS, OEM $73.69
NEC 16X Double Layer DVD±RW Drive, Black w/ Software, Model ND-3520A, OEM $66.49
Microsoft Windows XP HOME Edition With Service Pack 2 -OEM Specifications: Designed exclusivel...... $93.94
ImageQuest L90D+ 19" LCD Monitor w/ Speakers, 8ms and DVI ?RETAIL $388.00
Antec Solution Series Quiet Black Mid Tower Case with 350W Power Supply, Model "SLK2650-BQE" - Retail $45.50
$1,139.19
It's $15.99 to go from 754 to 939. Add another $29.01 to go from AGP to PCI-E on 939. Or, a grand total of $45 to go from 754 AGP to 939 PCI-E.
$45. That's it. While the performance increase with a 939 vs 754 may only be slight, is it worth an extra $45?
My opinion is yes.