Its usualy normal, as some monitors take its time to "wake up" if its been left to "sleep". What is the first screen that you see after your monitor displays? does your monitor light like on green (on) or sleep (orange, or blinking) at the 10-15 sec you described?
Bios could be contributing to it but i realy doubt it.. as it just does a POST check of all devices on the pc, then the 1 beep will tell you everything is OK.. turn that plug and play on again if you want, or load optimal settings..
try updating your drivers and firmwares, especialy for your monitor and graphics card if you realy think that its causing you that problem, or if you still think your mobo/bios is to blame, take a look at what bios flash update is available for your motherboard.. but be warned.. the flash may fail on you so follow their instructions exactly.. but other than that i'd just say bear with the slow startup..
hardware wise, you can check all cables connected properly, power ok etc.. usual troubleshooting stuff...