Headlamp - Silverstar 9003ST (60/55 watts)
Passing Lamp - Silverstar 893ST (37 watts)

some folks say they've had issues with the 893st fitting (depth) in the aux lamp housing but I didn't have any issues on my 09 ultra or my 12 ultra. slipped right in

 

had silverstar ultras in my 09 ultra for 3+ years without a problem.

I bought my 2004 Silverado 2500HD in 2006. Same Silverstar Ultra bulbs are in it today that I put in back then and let me tell you that is one rough riding truck.

never had a problem with either setups.

 

Here is my experience: I have found that replacement bulbs of stock wattage, in the 4500-6000k temp/color range, give me a nice "daylight" coloring at night with good contrast and definition. Bulbs with a temp/color rating in the 3500-4000k range tend to show a brownish-yellow tint while 7000k + makes the scene look unnatural and too bluish for good definition. With that said I also believe that going with a higher wattage bulb in an attempt to achieve more lighting is not a good choice as the support system of your lighting circuit is not designed for that heavy a load. The optional HD bulb has nice night-time lighting as does the Sylvania Ultra Star. My preference however is the H4 Nokia Ultra White rated at 6000k.

 

The dual bulb unit is built to be used on the HD's. Also sold by HD. You are right on the Kelvin colors. The Silverstar is a white, but not in the ultra white/blue range. I don't know the kelvin . The bulbs in the headlight I'm using are stock halogen. One is H9, I can't remember what the other is,(I think H11) but there is a Silverstar to replace them.
I like the Silverstar, but I have been WELL pleased with the stock that came in the unit.
The Silverstar I have had most trouble with are in my Dodge 2500. They have been replaced twice, & both seem to go out within about a month of each other. When I travel I have the lights on for extended periods which might be a strain on them. I seem to get around 60-65,000 miles on them. I have one that has failed on my Blazer at around 12,000 mi. The ones in the Harley haven't been in for long just about 2300miles, without a failure yet.
The H9 Silverstar is just a few more watts that the stock, I think around 70w, but much better light color. But I will have over 120 watts on high beam with them . Much better to see with than 65w single..... But that is just my opinion.........

 

I guess the H11 low beam is the only Silverstar available. Don't have one for the H9 high beam yet.

 

I buy minne at harbor Freight...

 

I recommend:
PIAA 70456 Xtreme White Plus H4 Anti-vibration Bulb [headlight]
PIAA 70822 881 Xtreme White PLUS 27W=50W Xtra Halogen Bulb, (Twin Pack) [driving lights]

About $100 for both items through Amazon. The light output is amazing at anytime of day. Perfectly white - I'm very happy with mine - installed on 2011 TriGlide

 

I installed the Silverstar 9003-st headlight bulb and the Silverstar 893-st in the driving lights this morning and I 'm pleased with the differance.Cost $65.00 total.and the brightness will get noticed in daylight by traffic coming at you as well as traffic pulling out of side roads I haven't had it out at night yet to check the down the road brightness.Very easy install but, the 893 bulbs are a little tight against the back of the chrone housing once it is hooked to the pigtail I will remove a little off the rear of the pig tail clip for a better seat in the chrome housing.Hopefully they wont cause a problem with smoking the lense up due to heat.