I have the following
Stiffi - single bore barrel & switch kit
Deadly Wind - use Freak kit
Stock Ego
Silhouette Switch Kit
Comments on them
Stiffi - single bore barrel, light and accurate, can be expensive to get all the bore sizes you need
Stiffi - switch kit - not enough bore switches (.695 available), light and accurate
Deadly Wind - use Freak, light, accurate, great if already own a Freak set
Stock Ego - obviously heavier than the carbon fibre barrels, good stock barrel
Silhouette Switch Kit - long backs, which do improve grouping / accuracy, nice carry bag, available in the Uk from both their site and LIPS
Recommendation is to consider Silhouette Products / Stiffi ahead other choices
LIPS are at every UKM, so you can judge for yourself