FLAC Question

Alot of my itunes collection is from uploading CDs, so its mostly mp3s with a bit rate of 128. now i want to convert some of them to flac so my question is should i just download them as flacs or should i just get an application like switch and convert them like that? is there a difference in sound between a file that i download as a flac and a flac file that was converted from a 128 mp3?
thanks in advance,
Lee

First off you should never... ever, ever, ever convert your cd's to MP3. If you must go the MP3 route, convert them to 320Kbps bit rate. At the lower 128Kbps it makes your songs sound metallic and crappy especially on hi-fi and club systems. I DJ so the higher bit rate and clarity in sound is extremely important to me.
IMHO... you should start off converting your CD's straight to FLAC or WAV. FLAC is a better quality file but the trade off is it will make your songs into bigger megabyte files:

128Kbps avg MP3=3-5MB vs 1035Kbps FLAC=10-15MB vs 1411Kbps .WAV=20MB

The 128Kbps MP3's you have will not sound any better if you plan on converting them to FLAC now. Basically garbage in, garbage out.
I hope this helps you out.