+10000000000 on the Apollo Quad and or the Apollo 16. We have both and believe me, the plugins from logic and Pro Tools stock and even Waves doesn't come close to the sound of UAD - 2 plugins! They are a bit pricey but worth every cent in spades
extremely low latency, Pro Tools Mode on the UA Console with full recall, tracking with up to 55 stereo plugins is AMAZING and the emulations of 1176/LA-2A/LA3A Studer Neve SSL etc etc etc is unbeatable and anyone who say they aren't one of the best plugins in the world honestly doesn't know what they are talking about. Regarding LS56/40 etc they are "good" but nowhere close to the Apollo Preams. You can set up a whole Headphone mix inside the Apollo Quad and Apollo 16 aswell as track with 1176:s and other amazing plugin emulations with basically 0 latency.
Very important: the plugins included with any UAD system like 1176/LA2 Verb and Pultec are called "Legacy" bundle and they are NOT what I am talking about here. You need to get the real bundles of these plugins from UA and not use the "legacy" plugins included, they sound "ok" but nothing more. Just an important thing as some might think those plugins included are what UA is all about but they are FAR from that. You can get started on them but as soon as you demo the real plugins from UA you will hear the difference all day long
And Apollo 16 and Quad have GREAT PREAMPS and as you can track with any of the UAD 2 plugins you will have a SWEET sounding system with the preamps on the unit. Preferably the Apollo Quad as it has 4 SUPERIOR preamps. The Apollo 16 has 16 ins and outs but no dedicated preamp like the Apollo Quad. The ULN is alsoma good product but the Motu and Focusrite are not in the same league. Not even close. Well worth the extra hundred bucks for the Apollo Quad!
Good Luck
Christopher