Big aint always best... Get yourself an amp with a decent dynamic range. Volume does not matter, that's what a PA is for. More important is to know the sound/sounds you want and employ an amplifier suitable for the purpose. This is not always as easy as it may sound, unless you have access to, and furthermore understand, the dynamic characteristic of the combined components of the amp. Building your own is an option not as difficult as it may sound, although it's not as cheap an option as it once was.

On the other hand, any decent Marshall, Vox or Orange will sound like the dog's bollox, whether miked up DI'd or big'N'bold centre stage.....

A really cheap option would be to use a proprietary pre-amp unit like the Marshall 9001 and stick it through the backline gear.

I have tried all the above, including building my own, and I found the best option to be...............
A Vox AC30, a quality mic and a PA with good speakers, sheer bliss!!!