Re: Bridge pickup for metal
I'd look at TB (trembucker) spacing, for most Ibanez guitars. If it's Fender or Floyd spaced bridge, you want a TB. TB-5 Custom is a great pickup for metal rhythm, and no slouch for other things. What comes across as sterile often depends on the guitar and amp.
For my tastes, I don't tend to get along with ceramic magnets, so I'd tend to swap out for an A8, particularly in the Custom. But that can be an oddly vintage metal tone, too mid-focused pickup for some tastes. But if Custom is too bright or bland, cheap to try.
If the guitar is bassy and tube screamer
Besides pickups, tube screamer is the standard into 5150-series input to tighten up bass for metal, set for 0-20% gain, unity or higher for output (60-70% pretty common), and tone to taste (usually not much more than halfway up). Parametric or graphic EQ in the effects loop is handy for a lot of metal rhythm tones, too. Can use both for mid-notch (narrower than scoop!) and to recover from cutting bass at pedal/preamp to reduce flub.
If pedal & EQ don't fix it, pickups are likely the culprit, and a lot of fans of tight rhythm don't get along with the Tone Zone. Any number of options, depends on your tastes. PATB-2 Parallel Axis Distortion is an awesome gonzo metal pickup, but possibly a bit bassier than you want, some rhythm players don't like that growl, and it also might be a tight fit if the pickup routes are small on the guitar, as it has a nonstandard bobbin shape (less rounded corners due to different polepiece shape). Custom, Black Winter, standard Distortion are all great choices depending on what character you want and how much you mind harsh high end (I find the presence on the standard Distortion rather unpleasant, though it's possible to control that with post EQ, and often is in recording studios).