Saturn does not need much mag, I have always found it to look great at around 120x in my 4.5" reflector because it would stay in the viewing field longer, I'd go with the 10mm eyepiece in the future,will give you 125x and should be a good complement for the telescope.
I am of the thinking that a 5mm eyepiece would be to much for the telescope right now and would rarely get used, besides if you get a 2x barlow the 10mm would effectively become a 5mm eyepiece but with a bigger exit lens.
Remember when buying eyepieces if you intend to get a 2x barlow also it would be a waste to get eyepieces that would be cancelled out by the barlow, just my thoughts.
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Rick M
http://groups.yahoo.com/group/AllAstronomyAllTheTime/

my astronomy & a.t.m. site
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