If I gave you a 20% pay increase, would that be piddly?
If your road tax went up 20% would that be piddly?
It doesn't really matter what the actual power figures are, it's the increase that's important. 20% increase in power on any given car should at the very least be easily noticeable. People put Mi16 engines into 205 GTi's - why bother - it's only about a 25% increase in power and doesn't even crack 200bhp. Why bother? How about going from XR3i to RS Turbo - a measly 23% or so, pointless.
Or, if you want something to relate to, if you upgrade from a Vauxhall 2.0 8 valve to an XE that's roughly 20% increase. So, a total waste of time and money eh?