I'm so confused now.
Should I get the OS and a amp like this
Or buy the Fostex Kanspea and this 2 watt/channel amp
Audio can be very confusing. Before 'hunting' learn the trade and yourself. Pick up test tones to get an idea what 30 Hz, 50 Hz, 80 Hz, 12,000 Hz, 15,000 Hz, etc. and a sound pressure meter ($40 from Radio Shack) to get an idea of what you want to shoot for in terms of loudness and frequency (I can't live without 'full' bass). Decide how you'll listen (desktop, small room, A/V, etc.) and adjust your amp/speaker selections accordingly (size, frequency, loudness) noting that the need for extreme loudness or deep bass reduce as listening distance reduce. Bring three or four of your favorite albums that represent the range of what you enjoy to audition a variety of systems in your price range (hopefully at a 'real' audio shop, not a huge warehouse where it won't sound like home even if you can hear over everything else). Good luck finding a tube amp to audition unless you in/close to a big city.
The biggest difference between the OS/Emotiva pairing and the Fostex/Bottlehead would be bass response (and cost). For me the Fostex 85 dB bass cutoff (except perhaps for desktop use) would be a no go (without adding a subwoofer), but taste do vary. On the other hand the Bottlehead should be more fun (better sound, more involvement).
Just to confuse you more, for desktop/small room use a better option in my opinion might very will be powered/active speakers (that have the manufacturer selected amp built into the speakers) which are gaining lots of attention for use with computer/bluetooth desktop/wireless users. Active speakers provide one channel of amplification per driver for enhanced dynamics, frequency response, and bass performance. In your $300 - 600 price range good choices for home use include (all 2-way designs that shouldn't overwhelm a desktop): $500 Adam F5 (active, lots of studio 'legs'); Audioengine A2 (compact/full sound); Emotiva Pro 5 (active, well reviewed); NuForce S3-BT (good bluetooth performance); Paradigm A2 (active, flexible); PSB Alpha PS1 (clear/pristine sound); and $500 Vanatoo Transparent One (includes a DAC).
