Tomato is, sadly, no longer under development, but still beats many modern router GUIs; it has features like live bandwidth graphs, dynamically updating device lists with signal strength meters, and more.
I've also been running a small home server for years, mostly as a file storage and backup-taking device, which ended up being a small 2010-era Acer Aspire Revo - a great little computer, but underpowered and with no extra internal hard drive space, so it sat on top of two external USB drives.
All of these had their own power adapters, and so the corner of my living room that housed all this equipment was a rats' nest of cables, not to mention the fact that I didn't have a wireless N network and that the Revo was underpowered enough that backups took ages to run, and trying to access its NFS or Samba shares incurred a couple of seconds' delay.
A plan forms
Now, I like nothing better than spending a day or two fiddling around with low-level Linux hacking, and so when a spare Shuttle case came into my possession I hatched a plan to replace everything with a single box - covering routing, wireless networking, file serving, backup-taking and other purposes.
Of course, the main requirements for a router are a machine with at least two network ports (one for the internal network, and one for the external network - I have a separate ADSL modem that plugs into). For access point duties, it needs at least one wireless card that supports Master mode - in my case, I have two Atheros wireless cards; one to run the 5GHz network, and one to run the 2.4Ghz network.
The Shuttle only has two PCI Express expansion slots, but it fortunately also has a mini-PCI Express slot on the motherboard; this meant I could add in a single network card to provide a second Ethernet port (the motherboard already has one), a PCI Express 5GHz-capable wireless card with three external aerials, and cheap 2.4GHz mini-PCI Express card with a large aerial that lives just inside the case.
In addition, the Shuttle has space for three 3.5" drives inside the case - I've put two hard drives and an SSD in there (there's actually space for a second SSD, too, as you can mount two in a single 3.5" slot).