Sounds about the same. Also had DX thumbies. Can't remember the stock saddle as I had the shop change mine for a Turbo before I took delivery. Think my stem was an Avenir one though - not a Zoom. Brahma bars didn't have Zoom on them, just 'Brahma Bar'. Does seem like a similar bike, but with slight frame and spec changes. The wheels sound the same as yours, Avenir rims on DX hubs and I think Tioga tyres (can't remember the model though). the fork was raked, but the fork tubes were a constant diameter along the whole length (no taper).
Mine had DX push-push STIs. Tyres were Panaracer Smokes (still got 'em). Fork was as you say - constant diameter, chunky things, that were raked / curved normally. Still got the stem, probably the handlebars (Avenir branded), and the seatpin (Avenir branded - it's on my hack bike).
Maybe it was a changover thing - I have the 91 brochure (which I will have got around the time of getting the bike), which my bike matched, but I bought the bike new in 92 (I think it was around March).
I remember newer bikes than mine having those brahma bars. Does anybody have the spec of 92 Diamondbacks - I always thought not much changed for 92.