2 x 60 Watt audio amplifier with 4 Ohm speakers
The largest cost in a DIY amplifier will be the enclosure if you want it to look halfway decent, then the transformer and heat sinks, etc. It also takes a long time to build. In your case I would advise a LM3886 chip amp, but read on...

Considering the speakers you are using, this isn't an audiophile project aiming for 0.00000 whatnot distortion, I'm sure you'd like something practical and decent sounding instead, with a minimum of fuss!

(Note: shopping questions are usually closed, so enjoy it while it lasts).

Get this, and a laptop power brick as a supply.

Rationale: the Chinese steamroller crushes everything in its path. Building your own is only worth it if you want world class audiophile hi-fi for ultra-megabuck speakers. This TI class D chip is known to work pretty well. And considering the price, honestly, why bother to drill a face plate and install connectors... drill &amp; tap the heat sink... Gaaah! This'll work, probably a lot better than you'd expect from the price...

Don't make a fuss about the RMS power, if you put the speakers on the desktop near your PC monitor, you won't exceed a few watts anyway, that should be pretty loud already.

However:

Check the Philips amp that comes with the speakers doesn't use an active crossover! If this is the case then the speakers are married with it and you won't be able to use another amp. A simple way to check is to count the wires in the cable from amp to speakers: 2 wires is passive crossover (OK with any amp), if more wires suspect active crossover.