Eternal Bow mod question

ok i have an Sundering Eternal bow of Fortitude with the following stats:

piercing damage 15-28 (Marks req. 9)
Damage+14 (when above 50%)
armor penetration+10 (chance 9%)
health+29

i cant inscribe it, so what can i do to mod it to get the max price for it. I Know it is a good bow (and would be better if i could inscribe it), but i want to make it better so i can get any more out of it. I dont really know mods so... could someone please help me out. (and if you know the price the mods run for, please fill me in so i dont get ripped)

The string and grip can be changed on ALL bows except green ones. This obviously isn't a green bow. Sundering is a max mod at 20/20, not 10/9, so I'm guessing you have had that bow since before they increased the numbers on Sundering. Fortitude is maxed at +30, not +29.

Intelligent people pay for a weapon based on the requirement and inscription or inherent mod, but the changeable mods. So the req 9 is great, and the 14^50 is almost max. 15^50 would get you more for the bow, but 14^50 won't be a HUGE drop in price. If you feel the need to improve the string and grip, get a 20/20 string and a +30 grip.

thanks a lot i will get to buying these mods. yes i have had the bow forever and was wanting to max it as much as i can and sell it to buy primeval for my dervish. Thanks tons!

sorry to say, but if you buy the mods, hen resell, the price will only go up by the price of the mods, and it wont get you your dervish's primevil

It's not going to make a big difference in the price to put mods on it. As Magma pointed out, people pay for the base requirement and the inherent mod (if it's not inscribable).
You could actually lose money in the long run by trying to mod it. The person you sell it to may not even want the mods you put on it - say, for example, a person wanted to use that bow with a [[Broad Head Arrow] based interrupt build - they may want the bow to have a Silencing string on it and maybe an Enchanting Grip (for whatever reason). They are not going to want to pay extra for the 20/20 string and +30 grip, which they'd have to change.
Also, Eternal bows don't sell for all that much anymore (especially not with a less-than-max inherent mod). You're not going to get a significant part of you armor budget out of it in any case.

Sell as is, Don't mod if you want to sell it, not going to get much if any more

First. Never buy mods for a weapon just to sell it, you wont increase the value of it.
Second. With a 14^50 mod you will probably have trouble getting more than 10K for it.