I am currently in the process of building a Lyra 8, just waiting for the circuit boards to arrive.
At first I considered building the Lyra 4 to save money but quickly realised that the amount of effort it takes to order all the parts really justifies getting a few extra parts to build the Lyra 8 instead. If you take ordering from different places and the shipping costs involved into account it is really less economical to build the Lyra 4 in my opinion.
Getting a faceplate and enclosure done for the Lyra 8 will naturally increase the overall cost but I still think it is worth considering the Lyra 8 if saving money is the only reason why you are attracted to the Lyra 4.
Essentially having two Lyra 4s in the Lyra 8 also greatly improves the instrument’s flexibility.