Yow! Is it any wonder I don't run IPFs?
Honestly, I've heard good reports from the field on them, but the Hellas cost about half as much, and I get my 90/130W H4s for about a third of the IPF. Susquehanna Motorsports -
www.rallylights.com. Tell 'em I sent ya!
Upgrading your harness depends on the year of your XJ and what you plan to do. I've got five RENIX, so I know them best - but the RENIX wiring handles 50/80W bults just fine (I calculated before I ordered...) without upgrading - but ChryCo got a little skimpy with the wiring and I'd not go more than stock in a 1991 or later (AMC did like to design for reliability.)
There are a couple headlamp harness upgrades out there, and I'm working on one myself, but I've been a little sidetracked lately, what with getting back into school and all. I'm taking this summer off, so I should be able to work out a prototype (finally!) and get some production drawings done for other projects I've got in mind, and work on the FAQ, and ...
Do pay attention to what the manufacturer of the upgrade harness gives for a rating, and select accordingly. One reason I'm designing my own is because I want to make it work for ANY H4 bulb you can find readily, and because I'm not wholly satisfied with the installation and construction of most of the other units (not saying they're built badly, but they aren't up to scratch as far as I'm concerned. I tend to design things to be a little tougher...)
Ordering from SMS will give you damn decent pricing - I get replacement bulbs from them, because (even factoring in shipping) they're cheaper than anyone local, including my "pet" parts house that gives me jobber pricing. They even beat International Truck on Fourth Street downtown - and that's hard to do, since IHC is a bigger distributor!
Before you order from RRO, do yourself a favour and peruse the SMS site. If you want to work on a tougher harness, link up with me one week-end and I'll help you get sorted out...
5-90