Buying an entry Mirrorless/DSLR

Hey guys!

I'd like to get a decent, more 'serious' camera without selling an arm or a leg (initial budget within €400-450, take European prices into consideration). I know the "what to buy" topics in this category are abundant and I've already read some of them, but I have some specific conditions which I'd like you to consider.

I already have some experience with more advanced photography and I played and shoot occasionally with cameras in this categories: my father's NEX-5R, cheaper/older Nikons (D3000, D80) and Canons (100D, some older Rebel).

I'm personally leaning towards mirrorless for convenience of reduced size and weight, but DSLRs are also an option if they offer significantly more bang for the buck.

Doing my research I see a lot of love towards Micro 4/3 as a whole system, it's supposedly best value for money. Thing is, I don't see myself expanding my privately owned gear a lot in at least couple years.
With that in mind, I'd have at least an occasional access to E-mount lenses owned by my father:

- kit Sony "pancake zoom" 16-50mm f/3.5-5.6 OSS
- Tamron 18-200mm f/3.5-6.3 Di III VC

My friends/family shoot both Canons and Nikons, but it's hard for me to tell which lenses they have & I wouldn't count on access to them at this point. I don't have any acquaintances with M4/3 or Fuji X, plus the latter are really out of my budget.

Naturally I am inclined to stay within the E-mount NEX/Alpha range, as I'm familiar (and satisfied) with results I had with NEX-5R and aforementioned lenses, especially the Tamron, though it is a big piece of kit.

That said, I was considering mainly NEX-3N and A3000, maybe an used NEX-5 (one of the variants, 5R probably)
A3000 gives me better ergonomics and a viewfinder, although a poor one, but with size and build quality as trade-offs. NEX-5 has good enough ergonomics and grip for me, but I'm afraid NEX-3N might be more difficult to handle, especially with the big Tamron lens. I'm not sure if NEX-5 is worth the premium over A3000 in this case as well.

What is your take on that dilemma? Maybe I should steer towards DSLRs after all?