Guidance on Which Arduino to Use


I am currently working on a project to read a spectrometer detector and to send the data using FTP.
I am using the Arduino Uno with the Arduino Ethernet Shield 2 (from Both have operating voltages of 5V.

My issue is that the code requires too much dynamic memory and program storage space is nearly maxed out. So I have considered switching to a different Arduino. Anything that has similar characteristics to the UNO (I do not need any more features or necessarily more speed although speed would be nice). One more note, I have quite a few peripheral components (16 Bit ADC, LCD from adafruit, power to the spectrometer, Chronodot RTC, and ethernet).

This leaves me with choices: Arduino Mega and the Arduino Due. I understand that the operating voltage on the Due is 3.3V while the operating voltage of the Ethernet Shield 2 is 5V.

Does this mean that I cannot use the Due for this project?

Would the Mega be the best bet here?

Also, I am confused about the Due operating voltage being 3.3V. I understand this means it cannot receive more than 3.3V to its pins, but does this mean that the HIGH output coming from its pins is at most 3.3V also or can it still deliver 5V output?

Thank you

Atmega1284. 16K SRAM, 128K flash. 32 IO.
I offer boards in numerous form factors,
This one is Uno-like. USB may offboard or onboard.

Thanks for the reply crossroads!

Just to clarify, when you say uno-like, does that include that the board will fit the shields the uno fits.