Do some reading here about different brands of aftermarket preamps and pickups to help narrow down what you might want to buy. What you select depends on what sound you want, what features you want (how much tone control, knob layout, types of coils etc.), and how much money you have. After that, you need to decide if you're going to DIY or have a shop do it. If you're not used to basic electronic work - simple mechanical assembly and soldering - you might want to have a shop do it.
The whole thing gets a bit harder if you're making changes to the design of the bass such that you have to re-route the pickup cavities or drill holes for knobs. If you start doing more extensive mods, then you might have to get some conductive cavity paint, rerouting grounding wires etc.
Ibanez seems to like to have non-standard sized pickups on many of it's basses so that's probably the first thing to check - does the size of the existing cavities match any of the aftermarket pickup sizes. After that, see what pickup matches the sound you think you want and what preamp might best go with if you want active. I prefer active because I like the tone controls better and the active output handles signal chain variations better (cable length, impedance, pedal impedance etc.). Passive is simpler and some prefer the tone over active.
I've found Ibanez basses to be excellent value for the mechanical quality of their builds and I like skinny necks. Their pickups aren't great unless you get into their higher end stuff where they use designs from reputable brands like bartolini and EMG so this is where you're likely to get the biggest improvements in tone IMHO.
I swapped Bartolini and Dimarzio pickups into two of my Ibanez basses and was pleased with the results. Neither brand was at the high dollar end of the after-market pickup options so something in the $200-$300 range for a pair of pickups might be what you'll spend unless you buy used. In both cases, I had to do some minor mods to the pickup cavities and everything was done with either a chisel or a dremel so I didn't have to buy a router.
Clubs: BTB 118, Ibanez 689, 5-string 436, P&W 820, Lefties who play Rightie 157
BTB675, EDB605, GSR200, Ibanez Promethean 210, GK MB500, OB-110
Last edited by Rob22315 : 12-20-2013 at 03:59 AM.