some hints on upping your bard's whoomph
Pick "Lingering Song" (makes your effects last 10 rounds after stopping, easily enough for most combats) complete adventurer IIRC) and "Music from the Heart" (increases Songs of courage's effects by +1; Eberron CS) both boost your music/performance significantly.
Combine with "Inspirational Boost" (SC).. for another +1 to all Song of Courage effects...
+3 to attack and damage for you and all your allies at 3rd level ? And what combat actually takes longer than 10 rounds - which would be the temporal limit for the Feat's effect ?
Too bad, "Power Attack" is inaccessible for you due to your low STR score - it does make for a wicked combiantion with the above, especially if picked with a two-handed weapon.
As for multiclassing, Rogue would probably not really be a useful choice, unless you plan to invest into Weapon Finesse to actually hit something.
PrC wise, take a look at the "Lyric Thaumaturge" in 'Complete Mage', which will upgrade your spellcasting prowess some and add additional spells known, from the entire sorcerer's/wizard's list no less. This also requires Melodic Casting mentioned above to qualify, though I would not pick it up before level 7 (to gain access to the "suggestion" song at bardic level 6).
Excellent mid-level feats are "Subsonics" (complete scoundrel, methinks) and "Doomspeaker" (FR- Champions of Ruin ) at 9th level (if you care to plan ahead that far )