will this work? I want to get some decent speakers for the sound bar, but dont want to upgrade the head unit yet. is this a good idea and are the speakers easy to install?

Speakers just basically plop in and plop out. Take maybe 30 mins to do. You can do them first and then do the head unit second.

Yep an easy install. One thing to keep in mind since you'll be running with the stock head unit... go for speakers with the highest "sensitivity" rating. For example: a 6.5" speaker (the best size for your soundbar) that has a 91 dB Sensitivity rating will sound noticeably louder at the same volume setting (requires less power to drive) than another speaker with only an 88 dB sensitivity rating... no matter what the speaker's wattage rating may be which is often so misleading that for a novice, it can ruin how good your system can sound.

Pay no attention to the huge hype advertising "150 WATTS!!!" or "200 WATTS" or whatever.... that is only the speaker's maximum power handling rating which is like saying a tire can go 150 or 200 mph... which doesn't matter if your rig can only go 50 mph.

Your stock head unit puts out such a small amount of watts that you need the speaker to be as sensitive to those watts as possible. Getting a speaker with a lower sensitivity rating can mean your head unit can't drive the speaker loudly enough without distorting.