I wasn't sure about the i5 though. Isn't that an old slow one?
Compared to i7, i9, and i10, yes. But in speaking of "at least this" vs "way overkill", the i5 is the minimum you should consider. The computer with the i7 has an i7 because I run Pro Tools on it and that is pretty much the minimum for Pro Tools.
I actually run Real Band down here on an i3 and don't have problems with it. When I ship the file upstairs it runs on the i7. I scratchpad down here and complete up there.
I don't particularly like laptops for creating music because the hard drives are typically cheaper hard drives that don't spin at the top RPM, often as slow as 5400, usually 7200. That comes into play if you are "under memoried" and the data coming across the data bus into the RAM will be a potential bottleneck. When you start adding tons of RAM to reduce the frequency of memory swapping to virtual RAM space, and then invest in SSDs, you need to start considering WHY you are spending money on a laptop at all??
Now for a laptop to take out to a gig where you are just playing back, you get to the "whatever" place. Playing back is nowhere near as CPU intensive as the crunching that goes into RB's track generating engine. I don't even understand why people insist on playing back multi track files in RB or BIAB when it's fed into a PA system that flattens those tracks out anyway. I just use WAV files when I go to a songwriter circle night. There is no need to care that the pedal steel track is on track 11. If you mixed it right, the pedal steel will be the right volume no matter what track it was on initially. So for computing power, it's horses for courses. Fit the computing power to the application. An i7 with a ton of ram just to play back WAV files is like buying a Maserati to drive to the store for milk.