Well, that sounds like PSU was not great if it affected overclocking. It really should not. Probably either old and partly faulty, or simply no good to begin with.
Most of the time "quality" of output (filtering, regulation, etc) does not depend on rated power and PSUs operate most efficiently at ~40-60% load, so too much overkill is not really beneficial.
That said finding good quality lower rated power supplies nowadays is not easy, so i generally stick to ~500-600W stuff which still exist.
Meanwhile i've found how to change multiplier and CPU voltage on ASUS A8N32-SLI Deluxe... exploring this BIOS feels like playing one of those old adventure games - cool &quiet has to be disabled, which unlocks an option in completely different place which, when enabled, shows multiplier and Vcore controls which are otherwise completely hidden (not locked -hidden). What confused me before is that there is separate option to bump Vcore by 0.2V which is always accessible - i though that's the only thing which was possible...
Dropped Vcore by 0.1V, left cool&quiet off, this resulted in lower temperatures than with cool&quiet. By default Vcore is slightly higher than it should be on this board - ~1.4V instead of 1.35. Sensor is completely unreliable - jumps all over the place by like 0.2V, ultimately had to use multimeter to confirm it is what it is set to and jumping is just the sensor - not actual voltage. And it is.
Also cut RPM sensor wire for zalman fan i am using for CPU cooler - it reports wildly varying inaccurate results (verified on different boards too), which sometimes causes "CPU fan error" message during POST.
Installed linux mint on the second SSD on this system in order to do TRIM, do backups without having to boot from thumb drive and transfer data over network. Second NIC this board has (pci-e marvel one) turned out to be quite handy - no need to mess with buggy nvidia one and its drivers. It works surprisingly well - apart from simple tasks i've mentioned it is possible to actually use firefox and browse the web including videos and such quite comfortably. This CPU being able to decode 1080P youtube with no hardware acceleration actually surprised me - many low end modern-ish systems struggle with this. 2GB of memory are not much, but SSD swap + vm.swappiness=99 along with memory management modern linux has work surprisingly well - 20-30 browser tabs before things start visibly slowing down. It is curious to see such an old system being able to perform modern tasks competently.
SSDs only work at sata1/sata150 speeds, but NCQ actually works and performance is quite good - i do not think it will be worth messing around to make it sata2 - will likely make no difference.
AthlonXP 2200+,ECS K7VTA3 V8.0,1GB,GF FX5900XT 128MB,Audigy 2 ZS
AthlonXP 3200+,Epox EP-8RDA3I,2GB,GF 7600GT 256MB,Audigy 4
Athlon64 x2 4800+,Asus A8N32-SLI Deluxe,2GB,GF 8800GT 1GB,Audigy 4
Core2Duo E8600,ECS G31T-M3,4GB,GF GTX660 2GB,Realtek ALC662