I've just done exactly that, also retired. Main use photography.
Spent a little more than necessary, but wanted a reasonable spec m/c. Went for the
Jeantec Aqua case
Asus M2NPV-VM motherboard
AMD Athlon 64 x 2 Dual Core 3800 AM2 CPU
4 gb ram. Photoshop CS2 & Lightroom, rather memory hungry.
ZALMAN CNPS 9500 AM2 - Processor cooler
Asus Extreme N6200TC/TD 256MB supporting 512MB DDR2 DVI PCI-E Graphics Card.
This cost me £407
I used my existing 2 x 2 Ide drives and 2 Sata drives + my existing 2 x DVD writers and also my memory card reader
Photoshop & Lightroom now a pleasure to use. The case looks rather snazzy also.