hey im lookign at a few amps and wana know if any of them have any particualr parts that replacing will really improve the amp. eg a genreally good amp but comes with a bad stocj speaker or tubes.

any info on the following would help:

Peavey vavleking
Fender blues Jr
Laney VC/LC 30
Peavey classic 30
Vox AC15

-im basicly trying to find an amp to buy but wondering if a cheaper amp with a few simple mods would be better than a more expensive amp. Also any other amp suggestionns would be great.