[snaky]

>You need to have multiple (powerful) machines for this

Oh really? For simple http 'hello world' comparision (where you are interested in relative numbers, not absolute ones) bechmark?

All you need is one old and slow laptop (with test contenders) and one modern and mighty (with test script). The only thing you have to be sure about is the test script can generate more load than test contenders can handle. Even if the old laptop isn't slow enough you can just add some predictable and stable load to cpu/disks/network/whatever is a bottleneck for them - you may use tools that are available for that or even quick & dirty hacks like one-liner 'while(1) {do some math}' that effectively make your 2-cores CPU 1-core while running with high system priority.