I'd honestly not try splashing out on anything, for example, I am currently running 15 year old genuine LR leads that have been in three vehicles and had multiple different ends crimped on to them - and still fine.
If you have specific leads that have failed, replace that lead, and then move on to the next problem. Same for the amp, try a known good one, people on this forum likely have spares kicking about you could buy/try for a tenth of the price.
When you have it running right then think about splashing out, until then you are basically firehosing money on to the project without a clear idea of what is wrong...
RPI like to trade on their reputation, but really most of their kit is overpriced, and their advice...... Can be questioned. They still recommend carbs, last I heard 🙄
All that said, if you want to spend money, there's no stopping you! But worth noting proper diagnosis is much better and cheaper than just shotgunning parts at a car.