If you really want to down size and are willing to give up some volume/bass in a small office consider powered, or better yet active, compact 2-way stand/desk mounted speakers. Note that these designs can have DSP (digital signal processing to improve crossover performance, extend bass at lower volumes, etc.) and DAC (digital to analog signal conversion) built-in. Prices are very competitive compared to passives (that have most of their money put into veneer). Just play your CD's through your computer or rip them using iTunes. I've been into stereo/audio for 40+ years and this is the direction I'm going in for my next 2nd system.
DAC technology is changing everyday, so either invest in a high quality unit such as Schiit BiFrost ($350) that is designed to be upgraded (one option is already available). Currently it's not easy to go much cheaper with comparable sound quality, but you could try and just plan on upgrading in the future. Control volume from the computer or from the speakers (some have front mounted volume controls).
Definitions:
Powered typically have a stereo amp built into one speaker. This amp has been selected/designed to match the speakers, otherwise similar to conventional passive speaker with separate amplification.
Actives have one channel of amplification per driver, again selected/designed to match and typically located inside the speaker cabinets. The crossover is before the amps in the signal path (allowing for a more sophisticated design and for the amps to see/react better/more efficiently to the drivers). Actives provide much improved dynamics, flatter frequency response, and incredibly deep bass for their size/cost.
Studio monitors are almost always active, but have a dry, un-involving sound, and are intended to find all the warts versus providing an enjoyable presentation. With the advent of computer/internet based sourcing more home use/audiophile powered/active options are being introduced.
Examples (none too big IMO for desktop use, but big enough for a small room), ranked by sound quality:
Vanatoo Transparent One - $500/pair, powered, response down to 49 Hz, $50 cherry option, honest use of DSP, analog and 24/96 digital inputs (DAC built into amp), rather well built
Emotiva 4 - $350/pair, active, response down to 58 Hz, ribbon tweeters, industrial looking, no grill, detailed sound, big soundstage, good value, front mounted volume control, add a DAC
Adam A3X - $650/pair, active, response down to 60 Hz, ribbon tweeters, rather industrial looking, no grill, professional studio monitors that sound really good (convincing, thrilling, un-diluted, super fine delineation of micro details, not sharp/harsh, highs are breathed, bass is tight/tuneful, single front mounted volume control (via their "Stereolink" feature), add a DAC
You can spend more on a system, but mostly you'd be getting nicer cabinets, deeper bass, and/or more volume.