I am only about halfway through the missions and everything is unlocked for me. Is there anything I can do with the left over honor I have?
It would be cool if there were some very expensive hulls or modules to purchase for later missions.
Have you unlocked the additional races as well as the various modules & hulls?
Yep, races too. Nothing left to unlock and sitting on over 100,000 honor now. I went through each mission on normal, hard and expert in order and had everything unlocked by halfway through. I’m still having fun, but it kind of takes something away when I don’t have any new items to work towards.
I’ll probably finish out the missions and start looking at the mods.
Allow me to compliment you on your skill – that’s really a masterful performance. I was considerably less agile at GSB than you when I was a n00b.
When you’re through with all of the remaining missions, be sure to introduce yourself over at the Modding forum. We can always use enthusiastic, talented players such as yourself. There’s a lot of good stuff completed and in progress over there, oh yes… 
Thanks for the compliment, but I didn’t say I won all the matches on the first go! A few of the experts matches took a couple swings. I’ll definitely try out some mods. Do you have any recommendations on which are more ‘polished’ than others?
Short answer:
I recommend starting with Legios. 
Long answer:
At this point in time, the Legios and Scavengers mods are among the oldest, most established mods. Eich does a lot of great work, and I recommend his mods. Legios is probably the most widely-played non-“other scifi franchise” mod. BTW, Eich is on hiatus for a few more weeks, but I expect him to come back soon with some tweaks for his existing mods as well as a status report on his newest work-in-progress, the Pirates mod.
Dantalion’s Star Wars Reloaded mod is generating a lot of buzz right now. It’s a retread of an orphaned mod and is pretty fun.
There’s also a mod inspired by Stargate, but it’s still quite incomplete.
The supernova which just rose on the horizon is Darkstar’s Unity mod. That must break the record for the mod with the longest uninterrupted dev time (four months!), and it is breathtaking – both gigantic and explosive. I’m not sure I’d recommend playing it until you’ve racked up some simluator hours on other mods first. The mini-Unity variant of his main mod is definitely not for the faint of heart, as it alters a fair bit of content in a vanilla install of the game.
I’m sure there’s other mods which I’m forgetting due to the outrageous lateness of the hour. 
We also have a lot of single modules (weaponry as well as regular items) that are available as ad-hoc solutions to various official limitations, as well as many additional ship types and cool homebrewed sprites.
There are many other mods existing in very incomplete stages. Some are available for download if you’re feeling brave and want to mess with the beta. Of the mods in that stage of completion, some aren’t much more than an intriguing concept yet while others are farther along but require polish. Perusing the Modding forum will give you a taste of what’s available and how far along it is. We tend to do a lot of mix-and-match modding…hell, one of our “Mod Patrol” crew even smoked out an unsuspected limit in the game once he installed enough mods that his copy of the game shot up above 500 or so discrete modules from all races (vanilla races as well as mod races). That was interesting…thank God that Cliffski fixed it, as the superb Unity mod would not have been possible without removing it.
I guess I may as well mention that I designed the very first dreadnaught-type cruisers for the game; page waaaay back in the Modding forum to find them. They’re conceptual substitutes for the battleship ship classes which Cliffski says GSB likely won’t have before GSB2 comes out (IF it ever does), so those DNs add some interesting fun to the four vanilla races. I’m a sucker for lumbering mobile fortresses of doom. 
Wow, thanks for the thorough reply!