Having been in essentially your same situation with wanting an "inbetween" for DOSbox, 9x, and 7/8 (I actually had some of the same games on my list too!) I settled on Windows XP with a few criteria based on my Windows 7 machine having previously run XP and having noted issues:
- Single-core, non-SMT CPU. This is an absolute must for some DX7-8 games, as some of them have issues with SMP or HT or what-have-you (usually they don't run stable, they run too fast, or they won't install). The Athlon64 or AthlonXP in your list would probably be the best choices here - I'd go with the Athlon64 if possible because it supports SSE2 and 3, and this can be a factor for some later games.
- Single GPU, non-USM, and not geared/optimized extensively for DX9 SM2+. Of the cards you've listed, the GeForce 4 Ti is the best possible choice. Multi-GPU systems (especially when it's a dual gpu card, where they're basically "locked" together) can cause troubles with un-optimized, old, etc games resulting in everything from constant crashes, on-screen glitches, very bad (unplayable) performance, etc.
I would avoid the 9800GX2, the P4 (if it's an HT model, unless you can live with turning that off and leaving it off), and the HD 4650 (especially if it's an AGP card 😵). I wouldn't even consider the Q6600.
I know, it isn't the "fastest possible machine" - but the bulk of the games you've got on your list will specify a mid-speed Pentium III as their CPU requirement, and usually list a 32MB graphics card or lower for GPU. The GF4 Ti will be powerful enough to get through most anything that you can't get working under 7/8 (I have yet to see a DX9 game that doesn't work on Vista-later, a few will require being run as administrator or other minor tweaks, but none out and out refuse to run or become BSoD factories), but if you want to run extremely high resolutions or with a lot of IQ, I would step up to a GeForce FX (I don't like suggesting Radeon 9 because of their heat/lifecycle/etc issues). GeForce 6 will be silly overkill for everything, but wouldn't be a bad choice if you want to christen the machine Ricky Bobby. 🤣
As far as the soundcard, the Audigy SE will be compatible and functional for what you need, but a "full" Audigy 2 ZS would likely be the best choice in terms of performance, compatibility, and stability (I *loathe* the X-Fi drivers so you won't see me suggesting one).
archsan wrote:
Higher quality? As in better DACs? Will there be discernible differences in sound quality? Or do you mean better build quality, better caps etc?
I'm curious about this too. The Elite Pro technically has the highest specs of any X-Fi (and measures as well as some true professional cards, according to ixbt), but it isn't like any of those 1-2 dB SNR differences or .000001% THD variations are going to result in some big, dramatic, glaring audible differences.