I just played a tune with the range of A3-D5 (I think that's the correct English terminology). When I started singing I had a problem with the A3. The last melodic lines is A3-C#4-D4. This seem lika a popular key (Dm) for this song even though A3 seem low for some men. I feel a bit embarrased how I can find this difficult. Do most men even sing this low? And is this A3 note easy since it is a part of that melosic line?
A3-D5 is a range accessible to contralto (low female voice) so I'll assume you are talking about A2-D4 instead. The lowest regular note for baritone (or choir "bass") tends to be about E2. The lowest regular note for a choir(?) tenor tends to be B2. Being a "lead quart" below the tonic, touching that note tends to be easier than more extended or elaborate uses of it since it's without accent and the following line and overall harmonic frame is idiomatic enough that not getting the pitch impeccably is less noticeable than with other uses.