i'm 100% sure he uses sony wrr and sony wrt wireless.
by the way i'm almost near steve harris rig:
MARSHALL 1960AV With EVM-12L
TRACE ELLIOT GP12X Preamp
C-AUDIO SR707 Power Amp
DBX-160A Compressor(Looking for 160)
Fender Precision bass 2009 Steve Harris
Well...
He used the Trace Elliot often in the 90s, but it seems that he phased out Trace Elliot in favor of his Electron preamp, which is modelled after a Hiwatt 200.
In an interview Steve said that an Ampeg SVT-CL is a regular amp that sounds closest to his custom rig.
Which I find strange myself, unless it might be that I don't know Ampeg that good. Not sure if an SVT-CL can go as clean and "hi-fi" (for a tube amp) as Steve Harris' sound.
And compressor... there are alternatives.
Stompbox: Maxon CP9PRO+ maybe, DBX based circuitry.
Probably as good as a rack DBX.
Maybe bongo can enlighten us on the hits and misses of DBX products, and what are better alternatives.
I went with the Maxon stombox for portability. So far, I am liking it (just got it 2 weeks.) Better controls than the CS-3 I was using.
Preamp... I hope the new Tech21 Leeds is very close.
I am going to get one.
I know Tech21 is good, I'm hoping the Leeds does the tonestack of Hiwatt well.
I thought about this too... but Steve Harris rig on a budget and portability for the weekend warrior.
Anyway, it's your prerogative to get his exact same gear.

Whatever makes you happy. And it will be great too.