On the internet people recommend stuff like the schiit jotunheim or the aune x1. Those devices are cool and all but what about the bigger stuff that's sold in audio stores? Like the marantz PM6006, or something like Pioneer VSX-330? I mean I have space on my desk so why not go for the bigger stuff?
Because they're speaker amps and most of them have crappy headphone driver circuits. Even among the best which basically routs the output stage on the amp to the front headphone jack have one disadvantage vs some dedicated headphone amplifiers: the latter since they're designed to run headphones, ie, not crank out as much power as a speaker, were engineered to run in Class A. The Marantz PM80 for example has a pure Class A mode, but in that setting it churns out only 10watts per channel, a small fraction of what it can spit out if you let it switch over into Class A/B, and yet it's the same size as the A/B topology amps. Marantz has decent headphone driver circuits but they still have one other problem: very high output impedance. Grados can sound like tin cans, AKGs can sound like tin cans with a low volume rumble with a hollow sounding bass drum, some other headphones can sound like a total mudslide. It depends on what amp - some amps will do the opposite on the same low impedance headphones.
One other thing that contributes to the size: the inputs and outputs. Newer speaker amps even if they're still Class A/B are smaller just by cutting down on these.
I mean I have space on my desk so why not go for the bigger stuff? I currently don't own any speakers, I only have my headphones but I am planning on getting some bookshelf speakers soon.
Because bigger doesn't mean better. Why buy a Class A/B amp that, at best, has a high output impedance even with all that power (that won't necessarily remain undistorted at 32ohms as its measurements at 8ohms suggest) when you can have something small and works better?
There are other ways to tackle having both headphones and speakers. If this is in a dedicated listening room and the headphones are only for when other people in the house are asleep, then get a good Marantz amplifier and an easy to drive, high impedance headphone, that way it won't have any difficulty driving that. Or connect a headphone amplifier to the Tape/Rec line level output on the amp.
In your case you're using a desk then you'd be sitting a lot closer to the speakers, you might as well get
nearfield speakers designed for listener at closer to 1m away from the speakers. Studio monitors are nearfield and have four channels of amplification - two channels in each cabinet, one for the tweeter and one for the midwoofer. Past room acoustics, this offers one important advantage: you can set the gain differently on each amp. Too bright? Lower the tweeter amps' gain. Too dark? Inrease the tweeter amps' gain.
You can get a headphone amp with a preamp output or DAC-HPamp-Preamp unit. Choose the right gear for the right headphones and they'll drive the headphones well, while allowing you to control the nearfield speakers' output using the same volume knob. AudioGD has DAC-HPamp-Preamp units that have an output selector switch out front so you don't even need to unplug the headphones to switch over to the speakers.
