[barx1963 (Malcolm)]

Mike
The two EPs you have and the 2x Barlow gives you 4 focal lengths and as your scopoe I believe is f/6 with a 1200mm focal length that gives you

25mm 48x
12.5mm 96x (using 25mm ep with barlow)
10mm 120x
5mm 240x using 10mm EP with barlow)

You will find that as you up the power, the views get a little less clear as atmospheric condition impact more. You will tend to get the best views most consistently with the 25mm. The stock 25mm EPs tend not to be too bad, a little sloppy at the edge of the field, but certainly usable.
The 10mm will probaly have a much smaller exit pupil and you will have to get your eye incloser to see the image. This makes it a little harder to use. For higher power views try the barlow first with the 25mm as this will preserve the eye relief and exit pupil of the 25mm EP.
I wouldn't rush out and buy EPs at this stage, and especially do not get sucked into buying an EP kit! Premium EPs are pricey and you are always better of learning to use the scope first with the low power ones, then decide what you want in a few months.

Malcolm