A good quality barlow will result in a negligible amount of light loss , and indeed in my opinion can even improve the image produced by some eyepieces. Regarding upgrading your eyepieces as previously stated the Explore Scientific 82 & 68 degree eyepieces are a great upgrade, although costly. If wanting to save money then the well tried and tested BST Starguiders are a solid choice, particularly the 5 - 8 - 12 - 15mm. What I discovered was that I wished I had bypassed the middle of the road eyepieces, and instead went straight to the better quality ones straight away. I would have saved a lot of money. Good luck with whichever direction you choose to go in, but replace your super 10 ASAP.