Kiddush Points

Tosfos in Pesachim (106a) ד"ה זכריהו has a discussion if kiddush on wine is a Torah law or not.  The Magen Avrohom (371:1) says since the conclusion is that is merely a Rabbinic law to say the kiddush on wine and one can fulfill the Biblical commandment of kiddush with the prayer services when one says מקדש השבת.  Rabbi Akiva Eger says based upon this that saying good Shabbos also would suffice to fulfill one's Biblical commandment for one has mentioned that the day is Shabbos.  In the Beur Halacha he objects to the R.A.E. because the Rambam says one needs to say דברי שבח in kiddush and that is not said by merely mentioning Shabbos?  The Rashba Teshuva (volume 4 #295) also says that one can fulfill kiddush outside the context of on a cup of wine or prayer but says it has to be words of שבח וקילוס. (In the sefer Ratz Katzvi he says the Rashba fits the R.A.E. not like the question of the Beur Halacha bit I don't understand how he reads the Rashba who says one needs words of praise?  Rav Mordechai Eliyahu also notes this Rashba sounds not like the R.A.E.)  The one asking the question to the Rashba however does indicate that merely saying today is Shabbos does suffice for kiddush which would fit with R.A.E.  What may be the underpinnings of this debate?  This blog in the past mentioned the machlokes Rambam and Ramban if the nature of kiddush is to mention and designate the holiness of Shabbos as a distinct day from other days or is it a human form of injecting kedusha into day like Beis Din declaring the shemittah year holy.  The Rambam goes lishitaso and hence requires a mention of the holiness and praise of the day. According to the Ramban however, one can argue that it merely suffices to declare that the day is Shabbos. 

The Dagul Marevavah (271:2) raises the issue if the the man of the house prays maariv and already fulfills his Biblical obligation of kiddush how can he recite kiddush for his wife who is obligated on a Biblical level if woman are not part of arvus (which he understands based upon a Rosh.)?  R.A.E. takes issue because of how he learns the Rosh.  However, according to R.A.E. the whole question shouldn't get off the ground because the woman should also fulfill her obligation by lighting neros Shabbos.  As pointed out even not according to the R.A.E., if a woman adds words of praise after lighting candles about Shabbos, they also would fulfill the Biblical obligation according to the Magen Avraham. 

The Mishna Berurah (271:2) takes issue with the Magen Avraham for mitzvot need kavanah to fulfill the obligation and one is not thinking of fulfilling the mitzvah of kiddush when davening?  The Chasam Sofer actually advises one to have in mind not to be yotzei kiddush in tefillah in order to be able to fulfill kiddush according to the takkanah of Chazal with wine in the place of the seudah (צ"ע if the chasam Sofer means to activly have this in mind ,this is what it sounds like from his haghos on Shulchan Aruch ,or this is automatic that one is not yotzei untill the meal after the takkana of Chazal, see his teshuva #17 and #21 he says it is like לב ב"ד מתנה שלא לצאת?)  However, as noted by Rav Shlomo Zalman in Shulchan Shlomo this is an interesting implementation of lack of kavanah.  The person that is davening is intending to say the words of praise about Shabbas, the same very same text as kiddush in fact, and he is expressing his his acknowledgment and intent of sanctifying Shabbos, why where is the lack of kavanah?  Says Rav Shlomo Zalman, because the person's intent is to say this as part of tefillah not as a fulfillment of kiddush.  It may very well be that the Magen Avraham will tell you there is no lack of kavanah here for the person has intent to do the same thing as kiddush does, the fact that there is no intent for the specific mitzvah of kiddush is not relevant.