32F411EDISCOVERY. Humm... Old design, and I doubt that this processor reaches 120 MHz.
All Nucleo and Disco boards from ST have a STLINK probe onboard (V2.1 ot V3). No need of a separate probe like the obsolete chineese STLINK-V2.
As you need a floating point unit and some mathematical libraries a Cortex_M4 or Cortex-M7 core will be more appropriate (The cortex-M3 is a M4 without FPU).
Most MCU have an I2S interfacace (included in the SPI interface).
What kind of LCD interface do you need?
If you need a sceen like a smart phone one, look at MCU with a LCD/FMC/MIPI interface and a graphical accelerator. This is the hard way...
For simpler displays you can use SPI or I2C or raw GPIO. Have a look at www site like Search Results for LCD - SparkFun Electronics. They provides many addon devices (LCD, SD slots...) and tutorials.
Some Disco boards have an onboard SD slot. This can be useful if you need a high throughput. Else a daughter board with a SD slot on SPI may be enough.
If you want an all in one board (MCU + screen + SD slot) go toa more advanced Disco boards. The drawback: these boards have many useless devices onboard.
In my opinion, if you are a beginner get a cheap board like NUCLEO with ST-LINK2-1 and start to evaluate the development load and the necessary capacities, experiment with the available libraries. Then you can more surely choose the final target.
Very important: choose a board with an available schematics.
Most (the older) NUCLEO boards have a STLINK-V2/1 which can be used to program other cards (a homemade card for example) with some jumpers to move. I find it very convenient to have an additional probe at hand.
The most recent boards with STLINK-V3 lacks this feature.
Now the choice is yours, it is difficult to advise you more precisely.
