o.k so you'll be selling off all your old models to buy a new army that you think will defeat everything. but what happens when that army fails your expectations? Logic dictates that it would just be cheaper to find a way to win with the army you have instead of starting a new one everytime you lose.
example: I started playing nurgle themed warriors of chaos army, and had a TON of losses while learning how my army worked, and how to actually win with my army. Archeon Can be beaten...I did it in a challenge with a simple nurgle lord. never fought Franz but I beat Kurt with the same Lord, if those guys keep popping up, have a strat to beat em down. no army out there will win just by showing up,find what your army does well and focus on that, then find out what your army sucks at and figure out a strat to compensate. example, my army is very infantry heavy, the units are meat grinders with legs, downsides are they have no ranged support are expensive and slow moving. solutions: grabbed a nurgle sorc to help wittle down enemy units as I advanced, got a nice banner to keep my front line from scattering, gave the large units mark of nurgle to protect from missle fire, and screened with chaos hounds, also added some cav to help the flanks. result: very nice list that my rivals like to play against, that does'nt rely on cheesey combos to win, just a solid plan and an understanding of what my army can and can't do. do I win everytime? hell no, but winning everytime is'nt that fun.We have an undefeated empire player in the club, he seems kinda bored and WANTS to be beaten(of course he ain't gonna just let ya do it), but it's still a blast to play against him(pun intended). bottom line, if you ain't having fun...take a stepback and see why. then come up with your solution.
anyway that's my two cents.