I have an 08 Masi Alare with Sora comonents. Would I be able to add 105's levers and everything still work fine or would I need 105 FD and RD as well?

Along the same lines, would I notice much by only changing the shifters or does the real improvements come from the drive train upgrades?

Thanks

The Sora you have is 8 speed and 105 is going to be 10 speed or 11 depending on what generation you get so it won't be compatible. You'd have to change the RD too and rear cassette and chain. Not worth the effort and expense for an entry level bike in my opinion. Nothing wrong with what you have now. If you want to upgrade look at a new or used complete bike with 105, Utegra or SRAM/Campy equivalent

You don't need to change the RD, just the cassette and chain, when you upgrade to 105 10s.

There are notable advantages in shifting when you upgrade the drivetrain (RD, FD, cassette, chain, crankset), but it comes with a compatible shifter as well. Better chain/sprocket engagement, better shifting upfront. Shifting will be even better with newer cables. The entire drivetrain is designed as a system to give good performance.

Why do you need to upgrade? Is the gear slowing you down? Or just have a hankering to upgrade?

IMO, it's not worth it to upgrade an entry-level bike. Ride it until it breaks then look for a used mid-level bike to upgrade to.

I really do not have a reason for the upgrade. Just have the itch I guess. You are correct, I just need to ride the wheels off of the thing and then I will deserve an upgrade to a whole new bike with better components.

I did a drive train and shifter upgrade on my synapse. Changed form 9 cassette to 10 cassette in the rear and made everything to the 105 level from the original sora and tiagra that came on the bike. I cost me about $250 in parts and $40 bucks in labor. The shifter I need was the biggest expense. A friend at my LBS hooked me up with a new left(front crank) shifter that he had missed matched and could not sell. I was having some shifting issues that spurred my upgrade, but I thinks if you can find a good deal on parts and plan on keeping the bike for a few years it is a worth while upgrade. It doesn't make you any faster but it does make for a more enjoyable ride.