CHRA for a k04-64 comes in at anywhere between $500 and $600 depending on where you get it. Not sure about other CHRAs, but if a slightly larger CHRA would fit into a k03 manifold and compressor housing it may be a really cost-effective way to add power. Best case scenario is you see performance a bit worse than the mk7 stage 2.
The rotating assembly in the IHI turbo you have is something a K04-026 could only dream about. If you're considering a compressor upgrade, don't go with something designed in the 1990s.
They're blown. Basically all you're buying is the exhaust manifold, compressor housing and DV relo kits. You still need to shell out $600 for the chra, $500+ for the tune, $40 for the install kit and whatever else. It's cheaper than the going rate for a used k04 but by maybe $200-$300 at best.