Hi there!

Well, first of all, I would be a little cautious going much above 140x with your scope. I know that the specs say the maximum magnification is 165x, but the general rule of thumb is to try not to go above 50x per inch of aperture (aperture is the width of front lens on your scope), or 2x per millimeter of aperture (so, for your scope, ~140x). So, since magnification depends on eyepiece focal length, the smallest focal length that you want to use with your scope is going to be about 6.4mm. Go any shorter than that and you'll probably just magnify a very blurry image. The only way to get more useful magnification than 140x is to get a telescope with more aperture (and then you'll hit a limit around 300x due to atmospheric distortions).

IMO, a barlow wouldn't do much for you at this point, as it would just give you one more magnification (180x), which is beyond the ~140x limit.

For eyepieces, it really just depends on what your budget is. For the most part, you get what you pay for with eyepieces (and pretty all much astronomical equipment in general). However, I will say this: if you feel this is a hobby that will last a long, long time, then investing in a high quality eyepiece might be a decent option for you, as you'll be able to use it with telescopes you might have in the future as well. Up to you.

One eyepiece that I could recommend to you is the Meade 4000 Series 6.4mm Plossl. This would provide 141x, so it'd be right at the limit of magnification. However, these Plossls with short focal lengths tend to have really short eye relief, which means you have to hold your eye very close to the eyepiece to see what you're looking at, which can be pretty uncomfortable. You can purchase this for ~$30 from Agena Astroproducts, or ~$34 from Amazon if you wish to purchase it there.

If you're willing to spend more, you could look at a Meade 5000 Series 6.5mm HD-60, which would provide 138x. This eyepiece has a bit more eye relief, and has a wider apparent field of view (you can Google info about wide vs narrow FOV). This is available for ~$80 from both Agena and Amazon.

If you really want a very nice eyepiece that you'd [probably] never really feel the need to replace, I'd take a look at the Explore Scientific 6.7mm 82 degree eyepiece, which would provide 134x. This is a very high quality eyepiece, and gives a very wide 80 degree apparent field of view (as opposed to a Plossl's 50 degrees or the HD-60's 60 degrees). Available from Agena for ~$140 or from Amazon for ~$145.

And of course there are other options - these are just the first three that came to mind.

Hope that helps! Be sure to ask any other questions you might have!