Actually, the one you have right now is good enough. The only other bows that I'd recommend are the Daedric Longbow, and the Bow of Shadows. One is found in Maelkashishi (with 11 Daedric Arrows), and the other is found in the Venim Ancestral Tomb.
There's also Auriel's Bow, but most people hand it over to Therana for the Feather-enchanted Daedric Cuirass/Greaves.
I remember readind somewhere that you can complete the auriel's bow quest without being in house telvanni...something about a guy in mounhold having the conversation topic "ash yams"...anyone know about this?
"Death is the greatest fate, for you know that every page has been read." Rogue267
Get Auriels Bow from Ralyn Othravel, then talk to the Mournhold museum curator, Torasa Aram, about it. Then go talk to Mistress Therana, and she will give you the enchanted Daedric Cuirass and Greeves for the bow.