What ballast are you running these on? I'm unclear, are you running a 175 se now, or are you going to darker bulbs in order to dim down the 250w that you're currently running?
If the former, I unfortunately don't have experience with any 175w fixtures: Bulbs are known for being very different even within the same brand, same kelvin, for different wattages and also for se vs de.
250w de mh on hqi ballast, I have run a few bulbs: I really like the Geisseman 250w de Megachrome Coral bulb, but it's expensive. I like the 250w Ushio 14k as well, but it's very white and if you are looking for something that has a blue tint, you probably wouldn't want it unsupplemented.
On a 400w blueline eballast I ran a radium 20k se, it was nice, but very blue.
Personally, I would get something with a color your like, but then still save up for a t5 actinic supplement... really nice not having to run the main lights 16 hours a day in order to enjoy viewing the aquarium. jmo
Alternatively, you could just do t5s, no halides, on a 30L.
-A