I use the house-brand of strings from
www.juststrings.com . On my five string Spector, I use custom guages that work out really great and an even tone across the board. They're also very reasonably priced! Go to their site and in the left menu, look for BULK STRINGS. Then click on bass and pick your fav's, nickel or stainless. I get nickel, because they are easier on my fingers and the frets.
Guages: 120, 105, 90, 70, 50
If you've got a 4-string, simply remove the 120. The 120 on the 5 string actually gives the bass more punch rather than using a 125 or 128. The thicker strings tend to get a bit muddy in some clubs. I've had good success with the 120.
I have attached a screen shot of my order for you to see an example. You get 6 strings in each pack of bulk string order. So if you figure this out... the order total is about $87, but then divide that by 6 and you are paying around $14 a pack!! Great deal, don't you agree?
Hopes this helps!