Gunbroker is a great tool for current pricing. I like to search the "Completed" sales and sort by number of bids from high to low. 5906's with more than 1 bid have recently sold from $265 to $755 (more or less) with a bunch starting with a "3".
The amount of LE sales of the 5906 has been at a steady pace and that does seem to be knocking down the prices. On the other hand, yours has the advantage of being a known quantity and with less risk than geting who knows what from a surplus seller.
I just looked at the "Completed" section (took me 1/2 hour to figure it out how to get there, duh!) and there where lots of 5906 for less than $350, and one had adjustable sights on it from what I could see, but it didn't say so in the descriptors.
If I had adjustable sights on my 5096 I never would have bought the 4006 with the adjustable sights.
I've seen the 5096 with adjustable sights go for $700.