Hi keyser_soze,
The HU has a 4ohm minimum impedance rating and is designed to generate it's maximum power output into 4ohms. As far as whether it will be able to drive 60W speakers or not doesn't depend on how much power the speaker is rated for but rather, if the speaker's sensitivity rating is high enough. Even a 20 watt speaker can have a low sensitivity rating, e.g., 68dB @1w/1m.; and most 'Cheap speakers do' as a result of the loose physical tolerances associated with pressed/stamped steel speaker frames, weak magnetic structure assemblies, poorly designed/wound voice-coil formers... etc. OTOH: a high performance pro-audio driver with a 700W RMS power rating can have very high sensitivity e.g., 105dB @1w/1m or more! My guess would be that... YES, the stock hu will drive those 60W aftermarket speakers with no problem because they're known to be of reasonably good quality!
This question is one that only you can answer. The way that you shop, and the way that you listen to your music will determine what would be right for you!
Best to you!
YES! The sensitivity is what you'll be looking for. Higher sensitivity means less power required for more volume, or less power required for same volume. I would strongly recommend going to crutchfield.com and chatting with an advisor (free) to get their take. They just helped me pick out some front door replacements on my daily driver (they arrive tomorrow).
Much of this will be driven from what type of music you listen to and if your objective is volume or clarity. Although not mutually exclusive, it's good to know your focus when purchasing. Because of my budget, the type of music I listen to, and my preference (clarity), I would save my money and wait until I could afford a full system replacement.
Alternatively, you could replace the head unit now and wire up everything so that there's easy access to the wiring for when you do your speakers later. Then you can take your time and buy/install one pair at a time when your budget allows later.
Good luck, and have fun.
