I've hardwired power cords and have installed IEC connectors, and in both cases installation is kinda messy. I prefer the hardwiring because of the sonic degradation involved with using an IEC connector. (I've never come across a high quality one, so Alexc's mention of the Furutech got my attention.) Of course you do give up the flexibility of being able to swap cords.
One thing that hasn't already been mentioned about hardwiring: It's likely the new cord will be thicker that the one you're replacing, in which case you might have to enlarge the hole in the chassis. Drilling the hole can be tricky, in that you'd be pushing the drill bit into the chassis, and if you go too far... well, let's not dwell on that... it's just that you have to be very careful. A simpler solution is to get a power cord that's not all that thick, e.g., I've had good success with a Stealh Audio FAC, a modest cord for low-level components such as CD players and preamps. I had to enlarge the inside of the plactic grommet that secured the cord to the chassis so that the FAC would fit through--that can be done with a file--but I didn't have to drill the hole in the chassis.
A simpler but more expensive option is to have your 555 modded (sacdmods.com, for example), and to get an IEC connector installed in the process.
One thing that hasn't already been mentioned about hardwiring: It's likely the new cord will be thicker that the one you're replacing, in which case you might have to enlarge the hole in the chassis. Drilling the hole can be tricky, in that you'd be pushing the drill bit into the chassis, and if you go too far... well, let's not dwell on that... it's just that you have to be very careful. A simpler solution is to get a power cord that's not all that thick, e.g., I've had good success with a Stealh Audio FAC, a modest cord for low-level components such as CD players and preamps. I had to enlarge the inside of the plactic grommet that secured the cord to the chassis so that the FAC would fit through--that can be done with a file--but I didn't have to drill the hole in the chassis.
A simpler but more expensive option is to have your 555 modded (sacdmods.com, for example), and to get an IEC connector installed in the process.