Equipment for giving instruments a louder/larger/fuller sound?

[Merzcat]

I have some Korg monotrons that sound too tiny, I want them to have a louder and richer sound.
What type of equipment should I get?

[Soloman Tump]

An overdrive pedal will give it a fuller sound.

I have an Electro Harmonix Crayon that gives a decent amount of gain together with versatile tone controls. 
Testing with my Monotron Duo and yep - lounder and richer. 

You could always try a distortion or fuzz pedal if you want a dirtier sound - or perhaps buy a pedal like a Boss DS-2 that will do Distortion and Overdrive well to a certain degree.

[Atrophist]

I use an Art Tube MP to boost my Monotron delay. They're cheap, available everywhere and can be used for just about anything.

[Eigen Bast]

overdrive, reverb, distortion...monotrons play very well with pedals and can pump out some seriously heavy sound.

[TheHandofLenin]

Elysia Karacter!

[Cementimental]

A half decent mixer


At one point I used to put my entire mix thru a clean tube Overdrive but never was totally sure if it really helped and it was too big a piece of gear so I sold it. But tube amps/pedals on general are worth looking out for

[urall]

i have a LEM Baby echo/mixer which does the job for me.

[Pigswill]

A stereo chorus would help here. Something like the Digitech Multi Chorus might be a good option (I see the prices are a bit high online right now, but a local music store or Craigslist might have one for ~$50)

[HONOR_IS_KING!]

DOD Meatbox will boost your volume on any signal.

Or get a cheap compressor and just pump up the volume.

[host body]

Learn how to record (gain staging essentially) and mix. EQ and compressor. Distortion will colour the sound at levels where it really fattens it up, if you want the clean synth sound just bigger use EQ and compression instead.