Eiruvin 63a - Giving All One's Tzedaka to One Poor Person

The gemara says that one who gives all his gifts to one kohein will bring famine into the world. The implication clearly is that one must distribute the matnos kehuna among multiple people. The Maharsha asks that throughout shas we find a concept of מכירי כהונה which means a kohein who is accustomed to always receiving the gifts from a particular person, clearly implying that this was an accepted system. The Maharsha suggests that perhaps the prohibition of giving all gifts to one kohein is only for a king like Dovid who presumably had enough to distribute to many kohanim. But for a regular person who generally has enough for only one kohein, he can always give everything to that kohein. However, the Maharsha points out that our gemara certainly doesn't seem to hold that because it makes a rule for everyone and not just for kings.

The Rashash points out that this halacha is not codified in the Rambam and suggests that perhaps it is because the concept of מכירי כהונה that we see throughout shas contradicts this gemara and overrides it. Based on the Rashash it would seem that lma'aseh it is fine to give all one's matnos kehuna to one kohein.

Would we apply this concept to tzedaka as well? Is there an issue with one who wants to give all his tzedaka to one particular poor person?

The Nodeh Beyehuda (kama, y.d. 81) uses this gemara as a source to not give sandakaos to the same person twice because there is a concept to distribute wealth and zechuyos to multiple people. If we would stretch this concept to sandakaos, it should certainly apply to tzedaka. The Nodeh Beyehuda seems to understand that we would pasken like this gemara and therefore we should say the same thing by tzedaka. Whereas, the Rashash seems to hold that we don't pasken like this gemara and therefore one can choose a poor person to whom he gives all his tzedaka.

The Magen Avrohom (Hil. Purim 695:12) writes that the reason that one must give matanos la'evyonim to two people as opposed to mishloach manos which is only to one person is because by aniyim there is a mitzvah to distribute to multiple aniyim rather than giving all the tzedaka to one individual. Presumably, the Magen Avrohom would draw his principal from our gemara, understanding that we do pasken like this, not like the Rashash. To elaborate on this point, the machatzis hashekel cites that Bach who says that if one has 100 gold coins, it's better to give 1 to 100 aniyim, rather than giving 100 to one because by giving to 100 aniyim you give life to 100 souls. The rationale that is offered by the Bach only makes sense if one would be giving a significant amount to each ani and enough to tend to their needs. However, if one has $100 which may be a significant give for 1 ani but not for 100, it would seem that even the bach and magen avrohom may agree that it is better to give it all to one person rather than distribute it to 100 poor people. The Pri Megadim seems to disagree with the magen avrohom and says that it is merely a technical diyuk from the pasuk which says matanos la'evyonim, implying multiple aniyim, but would not be a rule for tzedaka in general.
However, in Hilchos Tzedaka 257:9 the shulchan aruch writes that one should not give all his tzedaka to one poor person and the Be'er HaGola cites our gemara as the source. Clearly, the Shulchan Aruch holds that we do pasken like our gemara and doesn't consider the din of makirei kehuna to contradict it. Perhaps it is because makirei kehuna is assuming that one barely has enough matanos for one kohen, but if the has enough to provide many with a significant amount, he should be distributing his matanos and his tzedaka.