If the filter being discrete is your concern then externals would be best, although depending on what you want to keep may be a bit overkill.
I've only really used large external filters but all major brands have a wide range. You could look at Fluval 106/206, Tetra ex600/700 and Eheim Classic 2215/Ecco Pro 2234/Pro 3 2073.
Out of those I've only personally used the Eheim 2215, which I think is a great filter. A good simple design, proven reliability (something like 50 years of production?) and a massive amount of spares available. But I have used older Fluvals and various other Tetra and Eheim filter as well.
I've not got much experience with internals, other than Juwel ones and Eheim 2252 (way too powerful for your tank).