Okay thanks. Just few more questions.
1. Is there any sound samples of this preamp?
2. Can I just use a dpdt switch for switching and switch both input and output (for the preamp)?
3. Which chipamp kit do you recommend me to buy?
4. How I power all the amp parts from one source?
6. How much ohms the amp output (to know for the cabinet) will be?
7. Can I add a foot-switch to change between the channels?
8. Do you have any good guide for how to build a cab and how to choose speakers?

I prefer not to use the MG. I read little bit and though about one thing.

Build a chip amp kit.
Use a distortion pedal (Shredmaster) as a preamp.
Built another preamp for clean and put them on switch.

Also I wanted to ask is it better to read the amp handbook by j.darr or the book by temmu.

I have an MG15cd. I wanted you to give me possible project that I can make. I didn't really understood how to use the MG as a preamp. And in the second solutions you mean to put a dist pedal in the amp chaisis and use it like a second channel? Can I put a shredmaster clone inside and use it like a dist channel (but disable the tone controls of the clean channel while the dist is on)?

Well I want to build an amp with dist channel. I want to be like a normal tube amp just an a ss amp (I mean 2 channels, fx loop, tone controls, reverb, etc...)
I want mostly late 80's judas priest sound for the dist channel or at least as close as possible. I own a marshall mg and don't really like the sound of my dist (metalmuff) and I prefer not to use alot of pedals.

Hay I want to build a SS amp. It will be a big project and I am sure it will take some time. I want an amp that I can play a texas blues with. Good clean cause the drive I can get from an tube screamer. For the dist channel I want as close as to late 80s' judas priest sound.
I built some fx pedals and modded a cry baby. I think I will be able to build a head if I'll take it slowly.
Any suggestions what to do or to build?

BTW I want it to be able to hold on drums and to make some gigs (I think I need more than 50 or 100 watt)